2+2 =4 -2+3-1+2-4= whats the anwser

If a and b are the measures of two first quadrant angles and sin a = 4/9 and sin b = 2/5 find sin(a+b).

Which one ? is the answer and how to find this answer

Luke wants to reduce the area of his rectangular garden by 1/4 the expression 14/w can be used to represent this change. what is another way to write this expression?