x is 3 times the value of y, then x=3y;
y is 10 more than twice the value of X, then y= 10+2x.
{x=3y
{y=10+2x
Solve the system substituting the value of x in y:
{x=3y
{y=10+2(3y)
{x=3y
{y=10+6y
{x=3y
{y=-2
Now substitute the y to find x:
{x=3(-2)=-6
{y=-2