Math homework geometry please help

Answer:
A
Step-by-step explanation:
The theorem we use for this is
[tex]a(a + b) = c(c + d)[/tex]
Solve for d.
[tex]a(a + b) = c { }^{2} + cd[/tex]
[tex]a(a + b) - {c}^{2} [/tex]
[tex] \frac{a(a + b) - {c}^{2} }{c} [/tex]
A is the answer