Answer:
Eight less than the square of the sum of a number and seven:

Eleven more than the cube of a number:

Explanation:
First, find keywords...
Eight less than the square of the sum of a number and seven.
less than= subtraction
square= to the power of 2
the sum= the total amount resulting from addition
Now, start making the expression:
the sum of a number(x) and 7: x+7
squared:

Eight less = -8
so the expression is:

Find keywords in the next problem:
Eleven more than the cube of a number.
more than=addition
cube= to the power of 3
start making the expression:
the cube of a number(x):

eleven more than: +11
so the expression is:

Hope this helps!! <3