someone please help this is due in 25 minutes​

Because it is an isosceles triangle, the 2 sides that are given will be equal to each other.
15=4x+3
(subtract 3 on both sides)
12=4x
(divide by 4 on both sides)
x=3
Hope it helps!
Answer:
x = 3.
Step-by-step explanation:
1. 4x + 3 = 15
2. Subtract 3 from both sides.
3. Divide by 4 from both sides.