Yolanda's club has 35 members. it's rules require 60% of them must be present for any vote. at least how many members must be present to vote?

Ineed with number 17 i don’t get it at alll

Solve the system of equations. y= 2x y= x^2 - 15

Aright triangle has an area of 21 m2. the dimensions of the triangle are increased by a scale factor of 4. what is the area of the new triangle