Question 908155
a=1 b=1 c=0.75
1/a+1/b+1/c=1/x
1/1+1/1+1/.75=1/x
0.75/.75+.75/.75+1/.75=1/x
2.5/0.75=1/x
0.75/2.5=x
0.3 hours working together
check
1/a+1/b+1/c=1/x
1/1+1/1+1/0.75=1/0.3
0.75/0.75+0.75/0.75+1.0/0.75=1/0.3
2.5/0.75=1/0.3
0.75/2.5=0.3
0.3=0.3
ok