the total money spent by fred is 41.50 $
the cost of the pot is 29 $
and he buys plants of the remaining money
so, remaining money is, 41.50 - 29 = 12.50$
it is given that the cost of a plant is 2.50$
so, in 12.50$ the number of plant he bought is,
12.50/2.50 = 5 plants
thus, he bought 5 plants.