Respuesta :
3a + b = 54
Substitute b for 9
3a + 9 = 54
Subtract 9 to both sides
3a = 45
Divide 3 to both sides
a = 15
Substitute b for 9
3a + 9 = 54
Subtract 9 to both sides
3a = 45
Divide 3 to both sides
a = 15