4. 2/5 + 3/20= 8/20 + 3/20=11/20
5. 1/2 - (1/8+2/8) = 1/2 - 3/8 = 4/8 - 3/8= 1/8
6. 3/4 : 3/2 +5 = 3/4 * 2/3 + 5= 1/2 + 5= 5 1/2
7. (14/9+13/9)*3/5= 27/9 * 3/5= 3* 3/5= 1/5