Question 80293
from first equation you want to move 3y to the other side so technically you want to add 3y to both sides so that 3y on the left of equal signs becomes zero
{{{x-3y+3y=0+3y}}} so *** {{{x=3y}}}
now that you have a formula for x you have to substitute it in the second equation
{{{3(3y)+y=7}}}
{{{9y+y=7}}} so 9y+1y=10y, then
{{{10y=7}}} in order for you to get y by itself you have to divide both sides by 10, thus
{{{(10y)/10=7/10}}} two tens on the left cancel out and you are left with
{{{y=7/10}}}
now that you have a value for y go back to equation marked *** and substitute {{{7/10}}} for y to find the value for x, you get
{{{x=3(7/10)=21/10}}}

thus your answer is {{{x=21/10}}} and {{{y=7/10}}}

Good Luck