Find a circle = [] a triangle = [] a square = [] Two circles + three triangles = 51 three circles + two squares = 84 one square = two circles

Find a circle = [] a triangle = [] a square = [] Two circles + three triangles = 51 three circles + two squares = 84 one square = two circles

Let the circle be x, the triangle be y and the square be Z
2x+3y=51
3x+2z=84
z=2x
obtain
x=12
y=9
z=24