I see no LED here. There is a reverse biased zener diode though.When the output is fed back into the negative terminal like that, it is called a unity gain buffer amplifier, or just buffer amplifier. So the voltage at the (+) terminal is the same as the output voltage.
Not sure how your class treats LED's, but mine treated them like a voltage source. The flat side of the triangle is the positive end of the LED, and the pointed side of the triangle is negative, so the voltage in the (+) terminal of the op amp is -5 Volts (remember, the voltage across the 10k resistor connected to the (+) terminal is 0 because almost no current flows into the op amp terminals).
So the output voltage is also -5 volts since the (+) terminal voltage of a buffer amplifier is the same as its output voltage. And then you just use ohm's law to find the current.
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