Question

the sum of the digit of a two digit number is 7 if the digits are reversed the new number increased by 3 less than 4 times the original number find the original number

Answer 1

original number 10x + y
new number 10y + x
x + y = 7


10x + y = 10y + x + 3
10x -x + y -y = 10y -y + x -x + 3
9x = 9y + 3
x = y + 3

x + y = 7
(y+3) + y = 7
2y + 3 = 7
2y +3 -3 = 7 -3
2y = 4
2y/2 = 4/2
y = 2
x + y = 7
2 + y = 7
2 -2 + y = 7 -2
y = 5
x = 2