Please help me to solve this....

The average of two numbers is 81. The difference between the number is 26. What is the smaller number?

[ a+b ]/2 = 81

so
a+b = 162

but b = a+26
so
2 a + 26 = 162
2 a = 136
a = 68

the average of three number is 25. two of the numbers are 18 and 40 what is the third number?

To solve this question, we need to use a system of equations.

Let's assume the smaller number as 'x' and the larger number as 'y'.

From the given information, we know that the average of the two numbers is 81:

(x + y) / 2 = 81

We also know that the difference between the numbers is 26:

y - x = 26

Now, we can solve this system of equations to find the values of x and y.

First, we can rearrange the second equation to solve for y:

y = x + 26

Now, substitute this value of y in the first equation:

(x + (x + 26)) / 2 = 81

Simplifying further:

(2x + 26) / 2 = 81

Canceling out the denominator:

2x + 26 = 162

Subtracting 26 from both sides:

2x = 162 - 26

2x = 136

Dividing both sides by 2:

x = 68

So, the smaller number (x) is 68.