Practice for the LAMBDA unit on eight students' quiz scores. Two students missed a quiz, so their cells are blank: watch for them.
Before each task, decide the shape of the answer. One value per student down a column is BYROW or MAP. One value per quiz across a row is BYCOL. A running result is SCAN; a single result built step by step is REDUCE. A grid of a fixed size is MAKEARRAY. LET helps whenever the same piece appears twice.
=BYROW(B2:E9, LAMBDA(r, AVERAGE(r)))
=LET(avgs, BYROW(B2:E9, LAMBDA(r, AVERAGE(r))), FILTER(A2:A9, avgs>AVERAGE(avgs)))
Each student's average; the students above the class average.