Question

Y = +3 +x/2

X+ Y = 21

Answer 1

X+Y= 21
X= 21- Y

Y= + 3+X/2
Y= +3+ (21-Y)/2
Y= +3+21/2- Y/2
Y= +6+21/2 - Y/2
Y= 27/2 - Y/2
Y= 27-Y/2
Y.2= 27-Y
2Y = 27-Y
2Y+Y = 27
3Y = 27
Y= 27/9
Y=9

X= 21-Y
X= 21-9
X= 12