There were 3 boys for every 4 girls how many student i all went the trip

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).

Anyone know? is appreciated! will mark brainliest if correct!

Jamie went to home depot.she bought 25 bags of soil that cost $9 per bag.she bought 15 pots at $8 each, and she bought 23 bags of pebbles at $15 each.she used a coupon that gave her $5 off for every 100 dollars she spent. how much did jamie pay at the end?