What value of "p" makes the equation true ?

You buy 4 items that cost 2.69 14.45 8.05 13.95 what is the estimated total round to the nearest dollar

If f(x)=1/x and g(x)=x+4 which of the following is the graph

How do you figure out which order to do two step equations in? like which thing do you subtract/add/multiply/divide first? i understand that you do the opposite of whatever's shown on the opposite side, but when?