If (a+b)(a-b)=21,a+b=7 and a-b=3 what Is the value of a

Quadrilateral abcd in the figure below represents a scaled-down model of a walkway around a historic site. quadrilateral efgh represents the actual walkway. abcd is similar to efgh. what is the total length, in feet of the actual walkway?

Starting at home, emily traveled uphill to the hardware store for 606060 minutes at just 666 mph. she then traveled back home along the same path downhill at a speed of 121212 mph. what is her average speed for the entire trip from home to the hardware store and back?

Write 5(6x+4)-2(5x-2) in the form a(bx+c) where a,b and c integers and a> 1