7 and 7 same length,means 180° ÷3 because triangle is 180°. so one straight line is 180°, now you know the middle triangle is 60 per 1. 180°-102°-60° u will get the "sudut"(sorry malay,i dont know what english type@#$%&!) .and 180°-60°, that means 7x+4=180°-60°. so just finish that step! goodluck
