the function j(x)=39x is the number of jumping jacks you can do in x minutes how many can you do in 5 minutes'?
This is asking you to evaluate the function when x is 5...so all you do here is substitute 5 for x and simplify.. since the question defines "x" as the number of minutes...and j(x) represents the number of jumping jacks.
j(x) = 39x
j(5) = 39(5)
j(5) = 195 <--- answer...
So you do 195 jumping jacks in 5 minutes
I really hope this helps :)
