Eric practice a piano for a total of 8 hours. he practiced 1/4 of that time. how many hours did he practiced?

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

Prove that 16^4-2^13-4^5 is divisible by 11.

Ameteorologist is studying the monthly rainfall in a section of the brazilian rainforest. she recorded the monthly rainfall, in inches, for last year. they were: 10.4, 10.3, 11.7, 11.1, 8.0, 4.4, 2.6, 1.8, 2.5, 4.4, 7.3, 9.5 fill in the missing values in the formula. what is the variance?