Three digit numbers that the first number minus the second equals the second minus the third

On three examinations, Dana received scores of 84, 89, and 78. What score does Dana need on the fourth examination to raise his average to 85?

You have a Spanish meeting every forth day and a math club meeting every tenth day. Today you have both meetings. In how many days will you have both meetings on the same day again?

5.2 turned into a fraction in simplest form.

A certain laptop is really popular and sells for $199.99. Since sales are so good, the store raises the price by 13%. What is the cost of the laptop after the markup?

Which statement is correct? (2.06 times 10 Superscript negative 2 Baseline) (1.88 times 10 Superscript negative 1 Baseline) less-than StartFraction 7.69 times 10 Superscript negative 2 Baseline Over 2.