Total throws = 187
Let three throws = 3t
And
Seven throws = 7s
So
3t + 7s = 187 -------------- (1)
While total collected money = $57
Money for three throws = 1t
Money for seven throws = 2s
Hence
1t +2s = 57 ------------------(2)
Now solving both equations, so multiply second
equation by 3 and subtract it from equation (1);
Equation (2) becomes 3t + 6s = 171
While subtracting it from equation (1) gives the
final equation as below.
s = 16
Putting s = 16 in equation (2);
1t + (2x16) = 57
1t + 32 = 57
t = 25
Thus 25 people bought three throws and 16 people
bought seven throws.
As for 25 people having three throws = $25
And
16 people having seven throws = 2x16 = $32
So total earned money = 25 + 32 = $57
<span>Hence proved. </span>
