29×( 1+ 1/29)=x
x=29×30/29
x=30
(2) If there are X pieces in 50 yuan, then there are 3x/5 = 0.6x pieces in 100 yuan.
50×x+0.6x× 100 = 1 100
50x+60x= 1 100
1 10x = 1 100
x= 10
0.6x=6
50 yuan 10, 100 Yuan 6.
(3) 700× (1-9/10) = 70 (μ g)
(4) 22 ÷ (1-9/20) = 22 ÷ (11/20) = 40 (mg)