Answers to Pre-Algebra Math Problems

In pre-algebra, you'll be introduced to concepts like variables, expressions and exponents. If you'd like extra practice, complete the questions below. Answers and explanations are provided so that you can check your answers and correct any mistakes you've made.

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When Should I Use Answers to Pre-Algebra Problems?

Pre-algebra is an important subject because the concepts lay a foundation for later math classes, like algebra, trigonometry and calculus. If you are struggling and need answers to certain questions, some textbooks have solutions in the back of the book. It can be tempting to look at the answers before attempting the problem; however, keep in mind that you will not have an answer key on the test.

Although answers can be helpful when you are checking over your work, remember that if you get a question wrong, you should ask your teacher for help. Don't just replace your answer with the correct one. Below are practice problems and the corresponding solutions. Remember to solve the questions first and then check your answers using the explanations provided.

Practice Questions


1. Solve for x. 6/15 = x/7

2. One half of a number, x, is 80. What is x?

3. The product of a number, x, and 17 is 136. Solve for x.

4. 6.1 x 10^2

5. 1.92 x 10^2

6. -3(1 + x) = 15

7. 4 (3x + 2) = 30


1. To solve this proportion, cross multiply, so the equation should look like this: 15x = 42. Then solve for x by dividing both sides by 15. For this problem, x = 42/15.

2. The equation for this problem should look like this: 1/2(x) = 80. To solve for x, multiply both sides by 2 to cancel out the 1/2. For this problem, x = 160.

3. Written out, the equation is 17x = 136. Divide both sides by 17 to isolate the variable. The answer is x = 8.

4. Ten squared (10^2) is another way of writing 10 x 10, which equals 100. So, think of the problem like this: 6.1 x 100 = 610.

5. Solve this problem by multiplying 1.92 x 10^2, which equals 192.

6. This problem is more challenging because it requires you to solve for a variable and use the order of operations. Begin by distributing -3 to everything inside of the parentheses. The equation should look like this: -3 - 3x = 15. Isolate the variable by adding 3 to both sides, so -3x = 18. Then, divide both sides by -3, so x = -6.

7. Like the previous question, begin by distributing 4 to everything inside the parentheses: 12x + 8 = 30. Subtract 8 from both sides, so 12x = 22; then, divide both sides by 12 to isolate x. The answer is x = 22/12, which should be simplified to 11/6.

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