You need to use a couple IF statements embedded inside the first IF statement to use it as the teacher suggests.
So I don't do your exercise for you, first make an IF statement that prints an A if the grade is >= 85, or a B otherwise.
When that works, then replace the B option with another IF statement to print B if grade is >= 75, otherwise a C. When that works, replace the C option with one to print C if grade is >= 60, otherwise a D. Do it one more time to replace the D option with one to print D if grade is >=50, otherwise F.
Riser's choice is better in terms of flexibility and using the power of Excel, but to show the power of the IF statement (and this early in the session), this is probably what the teacher had in mind.
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-- Groucho Marx</font color=blue>