String a is 1 yard shorter than string b. string c is 1 ft 8 inches shorter than string b.
the total length of the three strings are 13 ft 4 inches. what is the length of string a

Let the length of string A be x
it is 1 yard = 3 ft shorter than string B
so length of string B = x+3

String C is 1ft 8 inches shorter than B,
so C = x+ 1ft 8 inch = x+ 1+ 2/3 ft.

Total  of A +B+C = 13ft 4inch = 13 + 1/3 ft.

x + x+3 + x+1+2/3 = 13 + 1/3
3x + 4 + 2/3 -1/3  = 13
3x  = 13 - 4- 1/3
3x = 9 -1/3
x = 3 -1/9
x = 3ft - 12/9 inches = 3 ft - 4/3 inches
x = 2.889 ft