Question 705167
Michael age x,
Monique age y.

"Today": x=y+6

"In three years...": (x+3)+(y+3)=54


Try substituting x from Today into the threemoreyears equation.
(y+6+3)+(y+3)=54
y+9+y+3-54=0
2y+12-54=0
y+6-27=0
y-21=0
y=21.  x=21+6=27