The height of building ramp is h = 2 foot.
The base of the building ramp is b = 4 foot.
The code for new bulding is,

Let the new base be x for new building code and height remain same h = 2.

So Carrie increase the base from 4 foot to 8 foot.
Detemine the adjustment in base.

Thus Carrie increase the base by 4 foot to meet the new code for the building.