There are a total of coins when dimes and nickels are combined. The total amount is 80 cents. How many dimes and nickels are there, respectively?

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

Parabolas y=−2x^2 and y=2x^2 +k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.

If the value of cos330°is√3/2 then find cos 165°.