Hallar un numero, cuyo duplo aumentado en 5 es a su cuadruplo disminuido en 5 como 5 es a 7

The number of 8th graders who responded to a poll of 6th grade and 8 th graders was one fourtg of the number of 6th graders whi responded if a total of 100 students responddd to the poll how many of the students responded were 6 th graders

Using elimination, what is -4x+2y=-12 4x+8y=-24

Square a has a side length of (2x-7) and square b has a side length of (-4x+18). how much bigger is the perimeter of square b than square a?and show all work! you so