Question

Bob installed new windows in his house which were advertised to cut his energy bill by 7.1% per month after installation. If his new energy bill was $315, what was his monthly bill before he installed the new windows?

Answer 1

His monthly bill before he installed the new windows was $339.074...

Step-by-step explanation

Suppose, his monthly bill before he installed the new windows was
`x` dollar.

As his energy bill was decreased by 7.1% per month after installation, so the amount of bill decreased
`=x*(7.1)/(100)=0.071x` dollar

Given that, his new energy bill was $315. So the equation will be...

`x-0.071x= 315\\ \\ 0.929x=315\\ \\ x=(315)/(0.929)=339.074....`

So, his monthly bill before he installed the new windows was $339.074...