Given
A massive light hangs over the table in Jeremy's dining room. The light is supported by four strong chains which make an angle of 72° with the horizontal.
The force in each chain is F=36.4 N.
To find
The mass of the light in kg
Step-by-step explanation
Let the mass of the light be m
The weight of the light acts downwards.
To balance thisi force the force on the string vertically upward is considered
In equillibrium

Conclusion
The mass of the light is 13.84 kg