Answer:
Its basically asking 6.50 / .75 which is 8.6 or you can round it to 8.7
Step-by-step explanation:
If the cost of one pen is x, the Sasha spend 3x, and Malachi spent 1x.
Sahsa spend 3x - 1x more than Malachi. So, Sasha spent 2x more than Malchi did for a pen.
Just plug in how much a pen costs into x to fi d the numerical answer. :)
It is already in identity.
cos (x - y) - cos (x + y) = 2 sin(x) sin (y)