Answer:
x = 4
Step-by-step explanation:
Using cosine triangle formula, we know that;
c² = a² + b² - 2ac(cos C)
From our diagram;
a = 2x
b = x + 1
c = 7
C = 60°
Thus;
7² = (2x)² + (x + 1)² - 2(2x)(x + 1)cos 60
49 = 4x² + (x² + 2x + 1) - (4x² + 4x)(0.5)
49 = 5x² + 2x + 1 - 2x² - 2x
3x² + 1 - 49 = 0
3x² - 48 = 0
3x² = 48
x² = 48/3
x² = 16
x = √16
x = 4
