#3 do 120 divided by 15 to get how fast he runs per mile (8 is the answer) so and for 6 miles that's 8x6 which means that answer is 48.
#4 the 20% off times $150 would be $30 off so the $35 off coupon would save you most.
#5 Do 157.5 divided by 35 which is 4.5 gallons needed.
#6 Do 200 students times 20% which would be 200x0.2 which is 40 students
#8 I got $30 by just doing random numbers times .2 (for the 20%)