Building a D flip-flop with two D inputs using 3 S-R latches
How to start:

Look up "Clocked SR latch" and understand it.

Look up "D type flip flop" and understand it.

Read the question which asks for an implementation which has 4 inputs D1,D2,C1,C2 and two outputs Q1 and Q2 which outputs the state of D1 on Q1 when C1 is pulsed and the state of D2 on Q2 when C2 is pulsed - all this made from 3 clocked SR latches. 

Get a pencil, paper, rubber and start drawing...