Step-by-step explanation:
5x-2y=10
x-y=-1
Addition method
multiply the second equation by -2 and add it to the first one
5x-2y=10
-2x+2y=2
Total 3x=12
Divide by sides by 3
x=4
Now multiply the second equation by -5 and add it to the first one
5x-2y=10
-5x+5y=5
3y=15
Divide both sides by 3
y=5
Solutions are x=4 and y=5
2nd method
if x-y=-1, so x=y-1
bring the value of x in the first equation
5(y-1)-2y=10
5y-5-2y=10
put the similar term together
3y=15
Divide both sides by 3
y=5
now bring the value of y in one of the equation
x-y=-1
so x-(5)=-1
x=-1+5
x=4
Solutions are x=4; y=5
