I believe the correct answer is he paid the right amount
You can download the answer here
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115% is the same as 1.15
some number = x
115% of some number is 120
1.15 of x is 120
1.15 * x = 120
x = 104.3478
<span>x ≈ 104.3</span>
Complete theh square
isolate x terms
factor out coefient of x^2 term
take 1/2 of 1st degree coefient and square it, add positive and negative inside parnthasees, expand
f(x)=(2x^2+12x)+7
f(x)=2(x^2+6x)+7
6/2=3, 3^2=9
f(x)=2(x^2+6x+9-9)+7
f(x)=2((x+3)^2-9)+7
f(x)=2(x+3)^2-19+7
f(x)=2(x+3)^2-12
