Question 389489
Let {{{t}}} = Juancho's time to paint a car
Then {{{(2/3)*t}}} = Jonathan's time to paint a car
{{{1/t + 1/(2t/3) = 1/12}}}
multiply both sides by {{{t}}}
{{{1 + 3/2 = t/12}}}
Multiply both sides by {{{12}}}
{{{12  + 18  = t}}}
{{{t = 30}}}
It takes him 30 hrs alone