To get 13/20 to a decimal, the denominator needs to be multiplied by 5 to make it 100. If you multiply the denominator, you also have the multiply the numerator to make it equal. 13 x 5 is 65. The fraction is 65/100, which is 0.65 in decimal form.
The amount of fish caught is at a constant decreasing rate of 17. 203-186=17, 186-169=17, 169-17=152. So all you have to do is subtract the constant rate from the last known number.
