Answer:
1/2
Explanation:
Well first lets break it down into steps!
We have 1 cake.
Brother ate: 1/8
Mom ate: 1/8
Dad ate: 1/4
Now we know that 1/8 + 1/8 = 1/4.
So her brother and mom combined ate 1/4th of the cake.
Her dad also ate 1/4th.
So we have 1 - (1/4) - (1/4) = 2/4 = 1/2.
1/2 of the cake is left.