a) f(-10)
meaning x = -10
the first subfunction applies only below that, namely x < -10.
the second subfunction does contain -10 in it since -10 ⩽ x ⩽ 10, so we use that one then,
x = -10, thus x² is (-10)², or 100.
b) f(10)
x = 10.
that will also be the second subfunction, since it's the one that contains 10, thus,
x = 10, x² is (10)² or 100.
c) f(11)
x = 11.
well, is not the second subfunction, since its domain goes up to 10, x⩽10.
looking at the third subfunction, that includes 11, since x > 10, thus,
x = 11,
(11)² + 10
121 + 10
131.