Asemicircular archway is built in front of a garden using 8 congruent granite tiles, as shown in the diagram. find the area of one of the tiles. round the answer to the nearest tenth

So there's 8 tiles.
Radius from archway to the outer edge would be : 7 +1 = 8ft

You can use this formula to count the area of semi circle : π r^2/2

A = 3.14 x 8ft^2 = 100.48 ft ^2
A = 3.14 x 7ft^2=  76.92  ft^2

100.48 - 76.92 = 23.55 ft^2

Then you have to divide it with the total tiles 
23.55/8 = 2.94 ft^2 per tile >> (rounded to nearest tenth)

hope this helps