X+3y=15 and 4x+2y=30

Subsitution

minus 3y from both sides in the first equatio

x=15-3y

subsitute 15-3y for x in other equation

4 (15-3y) + 2y=30

60-12y+2y=30

60-10y=30

minus 60 both sides

-10y=-30

divide both sides by - 10

y=3

sub back

x=15-3y

x=15-3 (3)

x=15-9

x=6

(x, y)

(6,3)