Question

x
$x + y = 20 \\ x - y = 21$

Answer 1

Hey friend

X+y=20. eq.1
X-Y=21. eq.2

Solving eq.1 and eq.2

2X=43
X=21.5

Substituting X=21.5 in eq.1

=21.5+Y=21
= Y= -0.5

Be perfectionist

Answer 2

x+y=20.....(1)
x-y=21......(2)
y=-1/2

Putting value of y=-1/2 in Eq(1]
x+y=20
x-1/2=20
x=20+1/2
x=40+1/2
x=41/2