Given that ABCD is a rhombus, what is the value of x?

Answer:
E. 18.6
Step-by-step explanation:
The diagonals of a rhombus bisect each other at right angles. The means all of the triangles shown are right triangles, and the two marked angles are complementary.
__
Complementary angles total 90°.
(x°) +(4x -3)° = 90° . . . . . the marked angles are complementary
5x = 93 . . . . . . . . . . . . divide by °, add 3
x = 93/5 = 18.6 . . . . . divide by the coefficient of x
The value of x is 18.6.