We have two right triangles and three different rectangles.
The formula of an area of a right triangle:

l₁, l₂ - legs
We have l₁ = 20cm and l₂ = 21cm. Substitute:

The formula of an area of a rectangle:

l - length
w - width
We have:
rectangle #1: l = 22cm, w = 29cm

rectangle #2: l = 22cm, w = 21cm

rectangle #3: l = 22cm, w = 20cm

The total Surface Area of the triangular prism:

Given:
y is directly proportional to x.
when 
To find:
The equation that connects y with x.
Solution:
It is given that, y is directly proportional to x. So,

...(i)
Where, k is the constant of proportionality.
We have,
when
. Substituting these values in (i), we get
Divide both sides by 5.
Substituting
in (i), we get
Therefore, the required equation is
.
Answer:
I believe it could be any number because:
let y=any number
x^2+10x+y=16+y
x^2+10x+y-y=16+y-y
x^2+10x=16
you can add any number to both side and not change the solution.