using the numbers 1, 6, 7, 8 I need two separate equations to equal 11 and 18.?

Question

Exponents can be used with the numbers 1,6, 7, 8

Answer 1

18=
18 * (7-6)

11=
8 + 7 - √16

These use all the numbers once. I assume that's what you wanted. [Using the numbers more or less than once each is trivial. e.g.,
18 = 6+7+8-1-1-1 (or just 18 !) and
11 = 8+7-6+1+1 (or just 11!) ]

Answer 2

But is one allowed to use any of the numbers
more than once?
For example 1+8+1+8 = 18
and 6+6-1 = 11.
Is that allowable?