Answer: Terry passed 16 science tests.
Step-by-step explanation: Given that by the end of the school year, Terry had passed 80% of his science tests and Terry failed 4 science tests.
We are to find the number of science tests that Terry passed.
Let x represents the total number of science tests that Terry appeared in.
Since he failed 4 science tests, so the number of science tests that Terry passes is given by
[tex](x-4).[/tex]
Since he passed 80% of his tests, so we get
[tex]80\%\times x=x-4\\\\\\\Rightarrow \dfrac{80}{100}\times x=x-4\\\\\\\Rightarrow \dfrac{4}{5}\times x=x-4\\\\\Rightarrow 4x=5x-20\\\\\Rightarrow 5x-4x=20\\\\\Rightarrow x=20.[/tex]
So, total number of science tests = 20.
Therefore, the number of science tests that Terry passed is given by
[tex]n=20-4=16.[/tex]
Thus, Terry passed 16 science tests.
