Question

a number of two digits of which ones digit exceed the tens digit by 1. The number itself is equal to four times the sum of its digits. Find the number.

Answer 1

let the two digit number be 10x+y
y is the digit at one's place and x is the digit at ten's place.
given x=y+1
and 10x+y=4(x+y)
substituting x =y+1 on both sides
10y+10+y=4(y+1+y)
11y+10=4(2y+1)
11y+10=8y+4
11y-8y=4-10
3y=-6
y=-2
x=y+1
x=-1
Then the two digit number is 10(-1)+(-2)
=-10-2
=-12
that's all....

Answer 2

please refer to this image for solution