# 9.6.3. Solving Two Equations in Two Variables, One Is of the First Degree, and the Other Is of the Second Degree

In a two-digit number, the units digit is

- A28
- B82
- C92
- D83

### Example

In a two-digit number, the units digit is

### Solution

Denote the tens digit of the number by

If the product of the digits is

This pair of equations can be solved by substitution. Substituting the expression for

This equation can be solved by factorisation.

But as

Now substitute this value of

The two-digit number is therefore 28.