The tens digit of a two-digit number is five more than the units digit. Seven times the sum of the digits of this number is 3 less than the number itself. Find the number.

43

Step-by-step explanation:

Let

The unit digit = x

The tens digit = y

The number = 10x + y

The tens digit of a two-digit number is five more than the units digit.

y = x + 5

Seven times the sum of the digits of this number is 3 less than the number itself.

7(x + y) = 10x + y - 3

7x + 7y = 10x + y - 3

Find the number.

We substitute x + 5 for y

7x + 7(x + 5) = 10x + (x + 5) - 3

7x + 7x + 35 = 10x + x + 5x - 3

14x + 35 = 11x + 5x - 3

Collect like terms

35 + 3 = 11x + 5x -14x

38 = 16x - 14x

38 = 2x

x = 38/2

x = 19

Solving for y

y = x + 5

y = 19 + 5

y = 24

The number = 19 + 24

= 43

well if he bought them at 5 cedis each sold them at 7 cedis each then he would make a profit of 2 cedis of each book. if in total he made 150 cedis profit that means he sold 75 books. he lost 12 books at the start so that means he originally bought a total of 82 books.

step-by-step explanation: