P = (a+b)*h:2
a = 2P:h-b
a = 176cm^2:8cm-13cm
a = 22cm-13cm=9cm
Sprawdzenie
P = (13cm+9cm)*8cm:2
P = 22cm*8cm:2 = 88cm^2
Krótsza podstawa ma 9cm
Pozdrawiam~Haruqe
