Question 923219
1/a+1/b=1/x
1/4-1/8=1/x
8/32-4/32=1/x
4/32=1/x
x=32/4
x=8 hours working together
check
x/a+x/b=1
x/4+x/-8=1
8/4-8/8=1
2-1=1
1=1
ok
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