Solution:

The tension 56.6 Newtons.

Since the mass is 10.0 kg, the weight is 98.0 N. Each cable must pull upwards with 49.0 N of force. Thus,

sine 60° = (49.0 N) / (Ftens).

Proper use of algebra leads to the equation

Ftens = (49.0 N) / [ sine 60° ] = 56.6 Newtons