Question

the sum of the digit of the two digit number is 7 if the digits are reversed the didi No digit increased by 3 less than 4 time the original number find the original number

Answer 1

let a = the 10's digit
let b = the units
then
10a + b = the number
:
Write an equation for each statement
:
The sum of the digits of a two-digit number is 7.
a + b = 7
b = (7-a), use this form for substitution
If the digits are reversed, the new number increased by 3 less than 4 times the original number.
10b + a = 4(10a + b) - 3
10b + a = 40a + 4b - 3
10b - 4b = 40a - a - 3
6b = 39a - 3
replace b with (7-a)
6(7-a) = 39a - 3
42 - 6a = 39a - 3
42 + 3 = 39a + 6a
45 = 45a
a = 1
then
b = 7 - 1
b = 6
:
Find the original: 16 
:
:
you should check this for yourself in the 2nd statement