So you start with $2.65 and a variable y. What we will do is work without the dollar and keep it for the end as it quite disturbs and work our way while keeping the y. So first we have 2.65. Now it rose by y so. The price = 2.65 + y. Then it dropped by 0.15. So 2.65 + y - 0.15. Here you see we have like terms so we reduce and get 2.50 + y. Now it rose by 0.05. So 2.50 + y + 0.05. Again, like terms, reduce. 2.55 + y. There you go with the answer.
slope is 3 because rise over run. Rise is 3 and run is 1. 3/1 is 3. and b= y-intercept and the poiunt wehre the line intercepts the y axis is 3. so your answer is y=3x+3