Can someone help me out?

see explanation

Step-by-step explanation:

15

The x- coordinate of E is the same as the vertex F

The y- coordinate of E is the same as the vertex G

E = (b, c )

The x- coordinate of D is the same as vertex G

The y- coordinate of D is the same as vertex F

D = (a, 0 )

16

The x - axis is an axis of symmetry in the rhombus , thus

D is a reflection of B so D = (0, b )

The y- axis is an axis of symmetry in the rhombus, thus

E is a reflection of C so E = (a, 0 )