How do you know when to use the less than symbol and when to use the less than or equal to symbol when writing an inequality for a situation? ​

This depends on the situation. For context, you use less than when your inequality CANNOT exceed more than.

You would use less than or equal to if your inequality can be equal to a number. Here's an example.

John needs to buy X oranges and Y apples. He can AT MOST buy 10 total fruits.

x + y (equal to or less than) 45

John needs to buy X oranges and Y apples. He CANNOT buy more than 10 total fruits.

x + y < 45

this is the formula: v = the value of investment at the end of the time period

p = the principal amount (the initial amount invested)

r = the annual interest rate

n = the annual frequency of compounding (how many times a year interest is added)

t = the number of years the money is invested

^ means raise to the power of