Someone help with my math!! pleasee<3 it involves graphing

Isee the amount was $90.00 then reduced to $75.00 , what is the percent ?

If a baby uses 15 diapers in 2 days how many diapers will the baby use in a year

Find the volume of the described solid.the solid lies between planes perpendicular to the x-axis at x = 0 and x=7. the cross sectionsperpendicular to the x-axis between these planes are squares whose bases run from the parabolay=-31x to the parabola y = 30/x.a) 441b) 147c) 864d) 882