Hello!
To solve for x, first, you need to use the distributive property. Then, you use SADMEP, which is subtraction, addition, division, multiplication, exponents and parentheses, when solving algebraic equations only.
3(x + 5) = 21 (use the distributive property)
3x + 15 = 21 (subtract 15 from both sides)
6 = 3x (divide both sides by 3)
x = 2
If you were to take a test or quiz, always check your work. In this case, we found that x = 2, so we should substitute 2 into the original equation and see if both sides are equivalent. Remember to use PEMDAS for this.
3(x + 5) = 21, x = 2
3((2) + 5) = 21
3(7) = 21
21 = 21 | This is equal!
Therefore, x = 2.