I am having great difficulty with this any help would be appreciated.

Write this expression in the form e^kx for a suitable constant k.?

(e^4x * e^6x)^3/5, 1/e-2^x

which expression, you appear to have two of them

I will do the first one:
(e^4x * e^6x)^3/5
= (e^(10x))^(3/5)
= e^(6x) , so the "suitable" constant k is 6

your second expression is much too ambiguous to attempt.
You will have to use brackets.

is it (1/e) - 2^x ? or

1/(e - 2^x) ? or

1/(e-2)^x ?