Thanks :)

Perimeter of a rectangle  = 2 [ Base + Height ]  .....so...

88  =  2 [ (x + 4) + ( x - 6) ]      divide both sides by 2 and simplify within the parentheses

44 = 2x - 2        add 2 to both sides

46  = 2x             divide both sides by 2

x  = 23

So.....  the base  = ( x + 4)  = ( 23 + 4)    =   27

And the height   =  ( x - 6)  =   ( 23 - 6 )  =  17