Respuesta :

Answer:

x = 15

Step-by-step explanation:

The equation for direct variation is

y = kx

y=21 when x=3

21 = k*3

Divide each side by 3

21/3 = 3k/3

7 =k

y = 7x

Let y=105

105 = 7*x

Divide by 7

105/7 = x

15 =x