<PRE><B>Question 1116632</B>
The formula, if properly written, is T=50+(N-40)/4
which should appear, {{{T=50+(N-40)/4}}}.


To solve for N,  just undo what has been done to it, and do this to BOTH sides of the equation. 



{{{N=4(T-50)+40}}}


Given is that you have T=58.  Substitute this and evaluate N.
72 chirps per minute.



---
To see every step,

{{{T=50+(N-40)/4}}}

{{{T-50=(N-40)/4}}}

{{{(4)(T-50)=4(N-40)/4}}}

{{{4(T-50)=N-40}}}

{{{4(T-50)+40=N-40+40}}}

{{{4(T-50)+40=N}}}

{{{N=4T-200+40}}}

{{{N=4T-160}}}

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