f(x) = -10
set the equation equal to -10 and solve for x:
-10 = -x-1
Add 1 to both sides:
-9 = -x
Divide both sides by -1:
x = 9
Remove these 7 guys from your number
so people who took buses are 318
now divide 318/6 to know how many phone did each bus have
300÷60 = 5
5 hours of commercials was watched