Sam has 42 coins that consisted of dimes and quarters for a total of $8.70. how many dimes and quarters did sam have?

I’m really confused and need your assist me with this question i’ve never been taught

What is the point of inflection for the function f(x)=2cos4x on the interval (0, pi/2)

Square a has a side length of (2x-7) and square b has a side length of (-4x+18). how much bigger is the perimeter of square b than square a?and show all work! you so