7 a) 3 i 1/2 *4 = 14 cm
b) 68 dm : 4 = 17dm
8 a) 2*2 i 1/4cm+ 2*6cm=4 i 1/2cm+12cm = 16 i 1/2cm^2
b) 2*13m+2*8m=26m+16m=42m^2
