Answer:
a) x+4
b) a = 1, b = 10
Explanation:
a) You can read the lenght of AB, which is 4 + x
b) The lenght of AD is 6+x
The area of the rectangle ABCD is lenght AB * lenght CD,
so (4+x)*(6+x) = 24 + 6x + 4x + x^2 = x^2 + 10x +24
Since this must equal 28, it follows that
x^2 + 10x + 24 = 28,
so 1*x^2 + 10x = 4
(note that 1*x^2 is just x^2)
so a = 1 and b = 10