use sine law. x = 16.3cm
Step-by-step explanation:
Since triangle angles add up to 180 deg
angle F = 180 -87 -40 = 53
side EF/ sin (angle G) = side EG / sin (angle F )
EF / sin(87) = 13 / sin(53)
EF = 13/sin(53) × sin(87)
EF = 16.3cm
