Please help, I don't understand it

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

What is always true when two whole numbers are subtracted?

Zack notices that segment nm and segment pq are congruent in the image below: which step could him determine if δnmo ≅δpqr by sas? (5 points) segment mo ≅ segment qr segment on ≅ segment qp ∠ n ≅ ∠ r ∠ o ≅ ∠ q