Jack M. answered 12/17/12
Keys to Chemistry, Calculus, Literature and More
Hello, Elasa ---
Look again at your equation. The 3 in front of the parentheses means that you have to multiply 3 times anything inside the parentheses. That is the distributive property.
Let's see how it works:
5x + 3(x + 4) = 28 Multiply 3 times x and 3 times +4, and remove the parentheses
5x + 3x + 12 = 28
Now add the 5x and 3x terms:
8x + 12 = 28
Subtract 12 from both sides:
8x = 16
Now divide both sides by 8 to leave a single x on the left:
x = 2
This is your solution. Check it by plugging 2 in for each x in the original:
5(2) + 3(2 + 4) = 28
10 + 3(6) = 28
10 + 18 = 28