The equations can be solved by the elimination method or the substitution method. The elimination method has been used by Jade.
Let's use the substitution method because one of the equations has a single variable.
color(blue)(-x) +4y = 24" " can be re-arranged to give: color(blue)((4y-24) = x
This means that color(blue)(x and (4y-24)) are interchangeable.
We have 2 equations with 2 unknowns:
" "6y +3color(blue)(x) = 18" and "color(blue)(x = 4y-24)
color(white)(xxxxxxx)darr
6y +3color(blue)((4y-24)) = 18" "larr replace x with (4y-24)
6y + 12y -72 = 18" "larr an equation with only y, solve it
18y =18+72
18y = 90
color(red)(y = 5)" but "x = 4color(red)(y)-24
color(white)(xxxxxxxxxxxxxxxxxxxx)x = 4color(red)((5))-24
color(white)(xxxxxxxxxxxxxxxxxxxx)x = 20-24
color(white)(xxxxxxxxxxxxxxxxxxxx)x = -4
x = -4 and y = 5
