Answer:
a +b = 2
Step-by-step explanation:
a +3 = 6
a = 6 -3
a = 3
Plugin a =3 in the equation,
a*b +5*a +3*b + 15 = 24
3b + 5*3 + 3b + 15 = 24
3b + 15 + 3b + 15 = 24 {combine like terms}
3b + 3b + 15 + 15 = 24
6b + 30 = 24 {Subtract 30 from both sides}
6b = 24 -30
6b = -6 {divide both sides by 6}
b = -6/6
b = -1
a + b = 3 + ( -1)
= 2
