Ateacher has 21 red pens if the ratio of red pens to blue pens she owned was 3: 1 how many pens did she have in total

In the triangle abc< angle c is a right angle. find the value of the trig function indicated. find tan a if a =12, b=5 a. 13/12 b. 12/13 c. 5/12 d.12/5

7x+8y=-18, 4x-9y=-3 solve the system of equations

Acompany that manufactures and sells guitars made changes in their product range. from the start they had 20 models. then they reduced the number of models to 15. as a result, the company enjoyed a 10% increase in turnover. - how much did the stock level change? in (%)