The price of a certain item was $10 in 1990 and it has gone up by $2 per year since 1990. If this trend continues, in what year will the price be $100?

On average the price increased $2, so $\displaystyle \frac{100 - 10}{2} = 45$

Hence 45 + 1990 = 2035

Graph
The figure above shows the graph of a quadratic function in the xy-plane. Of all the points (x, y) on the graph, for what value of x is the value of y greatest?

Somewhere between 3 and 7? Does it have to be a particular point between 3 and 7?

Perhaps I'm plain wrong?!