1. Since y in first equation is positive and y in second equation is negative, the easiest was to solve this system is: 3x+y+2x-y=5+10 5x=15 x=3
Now use the x to find y: 3*3+y=5 9+y=5 y=5-9 y=-4
2. You can either multiply the first equation by 2 so that we get the same numbers in front of the y but with different signs or simply express one of the variables and write it in second one. First way: 2x+2y=3 /*2(multyplying by 2)
4x+4y=6 (that's our first equation) x-4y=-1 (that's our second equation)
now we just add the equations: 4x+4y+x-4y=6+(-1) 5x=6-1 5x=5 x=1
now we find y: 1-4y=-1 -4y=-1-1 y=-2/-4 y=1/2
Second way: We express x from the second equation and get: x=-1+4y now we change x in the first equation with our new x: 2*(-1+4y)+2y=3 -2+8y+2y=3 10y=5 y=1/2
