Question 909333
Let Maria be x years now
Let her mom be y years now

In 4 years time, 
Maria's mother will be three times as old as Maria.
y+4=3(x+4)
y+4=3x+12
y-3x=8
y=3x+8...................(1)


 Six years ago,

 her mother was seven times as old as her. Find their present ages. 

y-6= 7(x-6)

y-6=7x-42
y-7x = -36..........................(2)
substitute y from (1)
3x+8-7x=-36
-4x=-28
/-4
x=7 Maria's age
plug x = 7 in (1)


y=3x+8
y=3*7+8
y=29........ mom's age