A 1.60-m-long string is under 27.0 N of tension. A pulse travels the length of the string in 57.0 ms.

What is the mass of the string? In grams

v = √(T/u)
velocity, v
Tenstion, T
mass per length, u

v = (1.60m)/(.057s) = 28.1m/s
Tension = 27.0N
Solve for mass per length
u = .034kg/m
u = m / L
L = 1.60m
Solve for mass
m = .0548kg

the speed of a wave in a string is directly proportional to the sqrt of the tension and inversely proportional to the sqrt of the linear density
or
v = sqrt(T/mu)
1.60 m / 0.0570 s = sqrt(27.0 / mu)
mu = 0.0343 kg/m
and
0.0343 kg/m * 1.60 m = 0.0549 kg or 54.9 g