Assume the following simple models for the diodes.
The pn junction diode is off if the voltage across it is less than 0.7 Volts.
When the the diode is on (conducting) its voltage is 0.7 Volts
The Schottky diode is off if the voltage across it is less than 0.3 Volts.
When the the diode is on (conducting) its voltage is 0.3 Volts
Assume the Schottky diode is on and the pn junction is off.
Then assume the voltage across the Schottky is 0.3 V and write a loop equation
10 - 0.3 = 1.1K*INo current flows in the pn junction since we have assumed it is off.
I = 9.7/1.1 mA
The voltage acrooss across the pn junction is
Vpn = 10 - 9.7/1.1 = 1.18VThis is not possible, since the pn junction turns on at 0.7 Volts. Therefore the assumption that the pn junction diode is off is wrong. Since the pn junction is on, its voltage is 0.7 volts.
The voltage across the schottky is 0.3 Volts.
The voltage across the pn junction is 0.7 Volts.
The current through the Schottky is (0.7-0.3)/100 = 4 mA.
The current through the pn junction is the current through the 1K resistor
minus the current through the Schottky.
Ipn = 9.3/1 - 4 = 5.3 mA