Solve by substitution

x+3y=7

2x-4y=24

X=10

y=-1

...

Frm Equation 1, X+3y=7, Make Y D Subject Of The Formula, Then Y=7-x/3 (eqn 3), Insert Eqn3 In Eqn 2, 2x-4 (7-x/3) = 24, Multiply Throughout By 3, 6x-4 (7-x) = 24, 6x-28+4x=72, Collect The Like Term, 10x=100, Divide Both Sides By 10, X=10. Substitute X=10 In Eqn 3, Y=7-x/3, Y=7 - (10) / 3, Y=7-10/3, Y=-3/3, Y=-1. X=10, Y=-1