Remember the formula for perimeter of a rectangle is
P = 2( l+w) where l is length and w is width
Assuming structure is garden and walkway
P = 2( x-3 + 2x+10)
Combine like terms
P = 2( 3x+7)
Distribute
P = 6x+14
The area of a rectangle is found by
A = l*w where l is length and w is width
A = ( x-3) ( 2x+10)
FOIL - first outer inner last
= 2x^2 +10x -6x -30
Combine like terms
=2x^2 +4x-30
Now we want the area of the garden
A = l*w where l is length and w is width
A = ( x-5) ( 2x+7)
FOIL - first outer inner last
= 2x^2 +7x -10x -35
Combine like terms
=2x^2 -3x-35
The area of the walkway is the area of the entire structure minus the area of the garden
=2x^2 +4x-30 - ( 2x^2 -3x-35)
Distribute the minus sign
2x^2 +4x-30 - 2x^2 +3x+35
Combine like terms
7x +5