Find the sum or difference. give your answer as a mixed number in simplest form. 5/6 - 7/12

Iam so stuck. what is the worked out answer for this question?

Click on the graphic until you find the right quotient. (36xa - 30xb) ÷ (-6x2)

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