Question

Solve the pair of equation 3x+4y=25,5x-4y=-9 by using substitution method

Answer 1

★ 3x +4y=25.

=>3x =25-4y

.°. x =25-4y/3. ............(1)

★ 5x-4y=-9

=>5(25-4y)/3-4y=-9.

=>125-20y/5-4y =-9.

=>125-20y-20y/5=-9.

=>125-40y=-45

=>40y=160

.°. y =4

.°. x =25-4y/3

=>x =25-16/3.

=>x=9/3

.°. x =3