Proszę o pomoc w zadaniu klasa 6

zadanie 10
Pole = 1/2 * 5 * 12
Pole = 5 * 6
Pole = 30cm2 (kwadratowych)
zadanie 11
a = 8dm
b = 4dm
P = 24dm2
P = 1/2(a+b)h
24 = 1/2 (8+4)h
24 = 6 * h
24 - 6 = h
h = 18
zadanie 12
P = 1/2 * d2 (do kwadratu)
P = 1/2 * 25
P = 12,5cm2