Can someone please help with algebra question ?

The width of the regatta lake shown

 consists of nine, 13.5 meter lanes.

 Each of the sloped lanes measures 7 meters.

 Determine the width of the lake floor.

 The width of the top is 9 ×13.5=121.5 m

 The sloped lanes are 7 m

 The depth is 5 m

 Assume this as a side view of the lake,

 whose top is 9*13.5 m, depth is 5m, sloped side is 7m:

 Each side section is a triangle h = 5, hypotenuse 7,

 so subtract 2*base If you form a triangle at the side.

 7^2 = 5^2 + x^2

 x^2 = 7^2 - 5^2

 x = √24 = 4.898979485566356 m

 2x = 9.797958971132712

 w = 121.5 - 9.797958971132712

 = 111.702.. m.                               

Despite your clarification of the handwriting, I am still 100% puzzled about what this question means.  I am sure that is also the reason why nobody has tried to answer it.