The amount of algae covering the smith's backyard pond doubled every day until it was completely covered in algae on day 30 of the month. on what day of that month was 75% of the pond algae-free?

Find and simplify an expression for the area of five rows of x squares with side lengths of x centimeters.

9/10 divide by -3/15 as a mixed number

White shapes and black shapes are used in a game. some of the shapes are circles. while the rest are squares. the ratio of the number of white shapes to the number of black shapes is 5: 11. the ratio of the number of white cicrles to the number of white squares is 3: 7. the ratio of the number of black circles to the number of black squres is 3: 8. work out what fraction of all the shapes are circles.