① 4 / 15 (1 and 4 / 9-3 / 2 × 5 / 6) + 5 / 6) + 5 / 6 ② 1:5 and 1:4 (1:2 × 1:3 + (1:8-1:4))

① 4 / 15 (1 and 4 / 9-3 / 2 × 5 / 6) + 5 / 6) + 5 / 6 ② 1:5 and 1:4 (1:2 × 1:3 + (1:8-1:4))

1. Simplification: (4 / 15) / (13 / 9-2 / 3 * 5 / 6) + 5 / 6
=（4/15）/（8/9）+5/6
=17/15
2. Simplification: (21 / 4) / (3 / 2 * 1 / 3 + 11 / 3-5 / 4)
=（21/4） /（5/8）
=42/5
There are specific steps

73.05-4.9-5.1-33.05 with simple calculation

73.05-4.9-5.1-33.05
=(73.05-33.05)-(4.9+5.1)
=40-10
=30
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1/3*5+1/5*7+1/7*9+1/9*11…… +Simple calculation of 1 / 73 * 75
Simple calculation,

1/3*5+1/5*7+1/7*9+1/9*11+1/73*75
=1/2[(1/3-1/5)+(1/5-1/7)+.(1/73-1/75)]
=1/2(1/3-1/5+1/5-1/7+1/7-.+1/73-1/75)
=1/2(1/3-1/75)
=1/2*(24/75)
= 1/2 x 8/25
=4/25