Respuesta :

Ar2ro
2a + 2b = The perimeter. You know one side (5cm) and the total perimeter (30cm)So your equation should be 2(5) + 2(b) = 30. From here you simply solve for "b"   2(b) = 30 -10     2(b) = 20     b = 20/2    b is equal to 10cm.