Inequality?

1/J + 1/10 =1/6

Solve for J:
1/10 + 1/J = 1/6

Bring 1/10 + 1/J together using the common denominator 10 J:
(J + 10)/(10 J) = 1/6

Cross multiply:
6 (J + 10) = 10 J

Expand out terms of the left-hand side:
6 J + 60 = 10 J

Subtract 10 J + 60 from both sides:
-4 J = -60

Divide both sides by -4:
J = 15 - hours that will take Jim to mow the lawn alone.

You can also do it a bit simpler this way:

1/j+1/10=1/6
1/j=1/6 - 1/10
1/j=[10 - 6] / 60
1/j = 4/60
1/j =1/15
J = 15 hours that will take Jim to mow the lawn alone.