How do you go from 98 to 720 using just one letter?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

On one occasion, A Boy collects 71 rupees in form of 20 paise and 25 paise. He collects a total of 324 coins.

Can you tell me how many 20-paisa and 25-paisa he got?

Baseball bat and ball cost $100. If the bat cost $99 more than the ball, what is the cost of each?

Replace each alphabet with the number (1-9) to make the below equation correct.

AB * C = DE - F = GH / I

Arrange the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 above and below the division line in a manner that the thus formed fractions equal to 1/3.

(You can use one number only once)

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

In the image below, can you find the value of an angle(y)

What is next number in the pattern below:

131 517 192 123 ?