Write it as an equation:
X - 10 = 6x + 3
Now solve for x:
Subtract 3 from both sides:
x-13 = 6x
Subtract 1 x from both sides:
-13 = 5x
Divide both sides by 5:
x = -13/5
Pythagorean theorem is

and using that sin is opposite/hypotenuse, you can find the third side of the triangle.

now you know adjacent is 60, so cos=60/61
The answer is 5900 as 879 in 5000 is closer to 900 rather than 800.
Y would equal -17! Good luck!