Loaded Voltage Divider
Break the circuit at AB, and obtain the Thevenin equivalent, consisting of Vth as the divider E with R1 and R2 and Rth as the parallel combination of R1 and R2. With this,
now you can solve for U as the divider of Vth, and Rth and RL..
If it is I you are solving for, then you know U, Vth, and the resistance between them to use ohms law to calculate I.