(1-3/7)k=2/7
1-3/7=4/7
4/7k=2/7
k=2/7×7/4
k=1/2
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13 4/5 b -3=8 1/2
69/5 b=8 1/2+3
b=23/2 × 5/69
b=5/6
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48 2/3t-4 1/6=8
146/3 t=8+4 1/6
t=73/6×3/146
t=1/4
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(3/8+4/3) x=4 5/9
3/8+4/3=9/24+32/24=41/24
41/24x=41
x=41×24/41
x=24
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8 4/7c+8=15 1/2
60/7 c= 15/2
c=15/2×7/60
c=7/8