Question 985522
The first truck can plow (1/30) of the lot per minute.
The second truck can plow (1/50) of the lot per minute

Together they can plow {{{(1/30) +(1/50)}}} of the lot per minute
{{{(1/30) + (1/50) = (5/150) + (3/150) = (8/150)}}} of the lot per minute

How long to to the whole lot?

{{{Time* (8/150) = 1}}}
{{{Time = 150/8 = 18.75}}} minutes
So it will take them 18 minutes and 45 seconds to plow it together