Question 1001143
Hi there,
Maria's Father is now twice as old as she is
F = 2M
16 years ago he was four times as old. 
F - 16 = 4(M - 16)
Replace 'F' with 2M from top equation.
2M - 16 = 4(M - 16)
2M - 16 = 4M - 64
Collect like terms
2M - 4M = - 64 + 16
-2M = -48
2M = 48
M = 24
Maria is 24 years old
Her father is 48 years old.
Hope this helps :-)