the cables are at an angle of 48.5 ° to the horizontal directions.How large is the force F1 exet on the trafic light if its mass 2.80 Kg

If F1 and F2 are at the same angle then they must have the same magnitude to prevent any horizontal movement.

The vertical components of force require that 2F1*sin(48.5) = 9.8*2.8

or:  F1 = 9.8*2.8/(2sin(48.5))

Can you take it from here?