help solve: if x in expression 12(x+3)+9 is increased by 9, how will the value change

Question

Im not understanding how to set this problem up. Im freshing up my math skills for my upcoming TEAS exam. Thank you for your time.

Answer 1

The easiest way to answer this is to put x=0 in the expression and evaluate it: 36+9=45.

Now put x=9 and evaluate it again: 144+9=153, which is bigger than 45 by 153-45=108.

Whenever x is increased by 9 the expression evaluates to 108 more.

To solve this algebraically work out 12(x+12)+9-(12(x+3)+9=12x+144+9-12x-36-9. Note that the constants 9 cancel out, and so do the 12x terms and we are left with 144-36=108. Note that 108 is 12×9. And 9 is the amount by which x was increased, and 12 is the multiplier outside the parentheses.