Answer:
Hey what'sup?
You need to dig a little in, for what it's actually meaning
Here the total is 720 right?
Which came from the materials and the labors work in hourly basis
So it's like
Cost of the material + no of hours = bill
We don't know what the no of hours are, so let's assume it as 'x'
Hence the required equation is
375+35*x=720
35*x = 720-375
35*x = 345
Therefore x=345/35 =9.8
Therefore they worked for 9.8 hours or approximately 10 hours
Peace out
Do you have the equation needed to solve for x?
The inequality would start out looking like this:

Now it's just a matter of solving the inequalities simultaneously. Get rid of the fraction by multiplying everything by 9:

Then distribute the 5 into the parenthesis:

Now add 160 everywhere:

and finally divide everything by 5:
-22<F<266
Its 1.4 just use a calculator