1)7 1/2 * 2 2/3=7*2+1/2 * 2*3+2/3 = 15/2 * 8/3 = 120 = 20
2)12 1/4 : 7/9= 12*4+1/4 :7/9= 49/9 * 9/7= 441/2/= 63*7/4*7= 63/4= 15 3/4
3)20 - 15 3/4= 20/1 - 15*4+3/4= 20/1 - 63/4= 4*20/4*1 - 1*63/1*4= 80/4 - 63/4= 17/4= 4 1/4
4)4 1/4 : 6= 4*4+1/4 :6/1= 17/4 * 1/6= 17/24
5)17/24 + 3 1/8= 17/24 + 3*8+1/8= 17/24 + 25/8= 17*1/24*1 + 25*3/8*3= 17/24 + 75/24= 17+75/24= 92/24= 23*4/6*4= 23/6= 3 5/6
6)3 5/6 + 52/7= 3*6+5/6 +52/7= 23/6 + 52/7= 7*23/7*6 + 6*52/6*7= 161/42 + 312/42= 473/42= 11 11/12