Current across a silicon diode
First of all, remove the diode.

Now you have two voltage sources, with two voltage dividers across them.

For each source+divider, calculate first the open circuit voltage (notice anything about the resistor values? you can do that in your head), and second the output impedance (OK, that will need a calculator). Looking up Thevenin's theorem could help here.

Now you have two effective voltages, and know their source impedance. Reconnect the diode.