does anyone know how to some 4,5,6?

Use the Law of CosinesNOTE: Please check my numbers.  The numbers were blurry in the picture.Answer:  4) b = 29.8                 5) a = 24.3                 6) C = 53.1° Step-by-step explanation:4)b² = a² + c² - 2ac · cos B    = (20)² + (25)² - 2(20)(25) · cos 82°    = 400 + 625 - 1000 (0.139)    = 888√b² = √888  b   ≈  29.85)a² = b² + c² - 2bc · cos A    = (18)² + (28)² - 2(18)(28) · cos 59°    = 324 + 784 - 1008 (0.515)    = 590.49√a² = √590.49  a   ≈  24.36)c² = a² + b² - 2ab · cos C15² = (15)² + (18)² - 2(15)(18) · cos C225 = 225 + 324 - 540 cos C[tex]\dfrac{-324}{-540} = \text{cos C}\\\\\\\dfrac{3}{5}=\text{cos C}\\\\\\cos^{-1}\bigg(\dfrac{3}{5}\bigg)=C[/tex]  53.1   ≈  C