Question

Use substitution to solve this linear system :

x+3y=7
5x-4y=-10

Answer 1

(1) x+3y=7
(2) 5x-4y= -10

from (1) we have:
x = 7 - 3y (1.1)

Plug (1.1) into (2) and we have:
5(7-3y)-4y= -10
35-15y-4y = -10
35 - 19y = -10
- 19y = -10 - 35
- 19y = -45

y = (-45) / (-19) = 45/19

use the result to find x with (1.1)

x = 7 - 3(45/19)
x = 7 - 135/19

x = (133-135) / 19 = -2 / 19



is that right?