Question 1024028
Hi there,
maria's father is now twice as old as she is.
F = 2M......(1)
16 years ago he was four times as old. 
F - 16 = 4(M - 16)......(2)
F - 16 = 4M - 64........(2)
Replace F in Eq(2) with 2M
from Eq(1)
2M - 16 = 4M - 64
Collect like terms
2M - 4M = - 64 + 16
-2M = -48
M = -48/-2
M = 24.
Maria is 24 years old
Father is 48 years old.
Hope this helps :-)