3x+7=3x+2 (cancel equal terms)
7=2 ( the statement is false)
So we know that the swimming pool is 15 by 7 meters wide.
15 times 7 is 105.
Now, a tile costs $6 and covers 1 square meter.
So, we should multiply 105 by 6, which would give us 630.
So, if I'm correct, the answer should be that it costs him $630 to install the tiles on the swimming pool.
(sorry if I'm incorrect)