X=5y+41

X+3y=-15

Substitution method

X = 5y + 41

x + 3y = - 15

(5y + 41) + 3y = - 15

(5y + 3y) + 41 = - 15

8y + 41 = - 15

- 41 - 41

8y = - 56

8 8

y = - 7

x = 5 (-7) + 41

x = - 35 + 41

x = 6

(x, y) = (6, - 7)

you substitute 5y+41 for x and get 5y+41+3y=-15 then you simplify by doing 8y+41=-51 subtract 41 from each side and divide by 8 to get y alone. That's how you get 11.5 for your answer.