Don’t follow the link he or she gave you.
True
<span>Cos(A+B)=CosACosB-SinASinB
therefore Cos(A+A)= CosACosA - SinASinA
= Cos^2A - Sin^2A</span>
It is given in the question that cost of pork is $7.99/kg.
It means cost of 1 kg pork is $7.99.
Cost of 2 kg of pork is

And cost of 3 kg of pork is

Therefore cost of 3.5 kg of pork is

To find the answer, to convert a improper into mixed, first take the denominator (9) and find how many times it can go into the numerator (16) FULLY. The answer is 1 time. 1 is the whole number. Then whatever is leftover is the new numerator, and the old denominator is the same. So your answer is 1 7/9
Hope this helps!
The answer is y=-3/2x +3 so D