Question

Solve this system of equations using substitution.

Answer 1

y=3x

x=-2y+70

x=-2(3x)+70

x=-6x+70

collect like terms

Answer 2

y = 30, x = 10

Explanation:

y = 3x...eqn i

x = -2y + 70...eqn ii

Now,

Substituting eqn i in eqn ii,

x = -2y + 70

or, x = -2(3x) + 70

or, x = -6x + 70

or, x + 6x = 70

or, 7x = 70

so, x = 10

Now,

y = 3x = 3 * 10 = 30