The question tells us that the Eiffel tower will still be taller than Big Ben, even if Big Ben was multiplied 3 times. So lets work that out first.
Big Ben's height = 316 ft.
316 x 3 = 948 ft.
However the Eiffel tower is 38 ft taller than this.
So we add 38ft to 948 to find the Eiffel Tower's height.
948 + 38 = 986ft
Eiffel Tower = 986ft tall.