Answer:
x = 10
Step-by-step explanation:
All sides are equal in rhombus
3x - 11 = x +9
3x - x = 9 +11
2x = 20
x = 20/2
10
First you set 3x - 11 to x + 9
Than subtract x from both sides.
Than add 11 to both sides.
Than divide both sides by 2.
3x - 11 = x + 9
2x - 11 = 9
