let us solve for unit’* place,
B + 7 = A
And for ten’* place,
A + 3 = 9
Which means that A = 6 and B = -1 which is not possible.
So, there should be one carry in ten’* place, which means B + 7 >9
Now solving for ten’* place with one carry,
A +3 +1
= 9
A = 9-4
= 5
For unit’ place subtracting 10 as one carry is given to ten’ place,
B + 7 – 10
= 5
B = 5+10 -7
= 8
∴ A = 5 and B = 8
