The annual return percentages will be evaluated using the formula:
A=P(1+r/100)^n
where:
A=amount
P=principle
r=rate
n=time
a] A=$500, P=$400, n=1 years
500=400(1+r)^1
solving for r we shall obtain:
1.25=1+r
hence
r=1.25-1
r==0.25
annual rate of investment is 25%
b] A=2500+100=$2600, P=$ 2000, n=1 year
hence
2600=2000(1+r)^1
2600/2000=1+r
1.3=1+r
r=1.3-1
r=0.3 
annual rate of investment is 30%
        
             
        
        
        
Answer:
Step-by-step explanation:
c + f = 16......c = 16 - f
340c + 910f = 9430
340(16 - f) + 910f = 9430
5440 - 340f + 910f = 9430
-340f + 910f = 9430 - 5440
570f = 3990
f = 3990/570
f = 7 <====== 7 first class tickets bought
c + f = 16
c + 7 = 16
c = 16 - 7
c = 9 <====== 9 coach tickets bought