Question 28897
2X+Y=10 & Y=12X SUBSTITUTE 12X FOR Y IN THE FIRST EQUATION

2X+12X=10 OR 14X=10 OR X=10/14 NOW SUBSTITUTE 10/14 FOR X IN THE EQUATION 

2X+Y=10 OR 2(10/14)+Y=10 OR 20/14+Y=10 Y=10-20/14 OR Y=(140-20)/14 OR 

Y=120/14

PROOF 2(10/14)+(120/14)=10 OR 20/14+120/14=10 OR 140/14=10 OR 10=10

      120/14=12(10/14) OR 120/14=120/14.