Is sqrt(1 - sin^2 θ) = cos θ true? if so, in which quadrants does angle θ terminate?

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827

Aretha wanted to gather data about the cost of local bowling leagues in her area. she plotted the data and determined that the average bowling league costs consist of a one-time registration fee and a monthly fee modeled by the equation y = 15x + 20. identify and interpret the y-intercept in this model. the y-intercept is 20. this is the cost per month. the y-intercept is 20. this is the cost of registration. the y-intercept is 15. this is the cost of registration. the y-intercept is 15. this is the cost per month.

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?