Simultaneous equations
4x + 7y= 1
3x +10y=15

(-3)×  (4x+7y=1)                    -12x-21y=-3                  
   4×  (3x+10y=15)                  12x+40y=60      ⇒      (x s cancel out) 

-21y=-3
40y=60        ⇒19y-57
                    y=3
for find the x plug in the 3  to the y one of these two equations and solve for the x

12x+40(3)=60
12x=-60
x=5                  HOPE IT HELPS:)

We are going to be adding the two equations and want to cancel something out to isolate the other.
Let's cancel out the x term first
Multiply the first equation by -3 and the second equation by 4
-3(4x+7y)=-3(1) => -12x-21y=-3
4(3x+10y)=4(15) => 12x+40y=60
Add the two equations and the x terms cancel out, leaving 19y=57
y=57/9=3
Substitute that into the second equation and you get
3x+10(3)=15
3x+30=15
3x=-15
X=-15/3=-5
Final
x=-5
y=3