Question 913152
1/a+1/b=1/x
1/45+1/75=1/x
75/3375+45/3375=1/x
120/3375=1/x
x=3375/120
x=28.125 minutes working together
check
x/a+x/b=1
x/45+x/75=1
28.125/45+28.125/75=1
0.625+0.375=1
1.0=1
ok
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