Answer
$g_c=\frac{b_t-y_s}{r_r}$
Work Step by Step
$b_t=$ Blue triangle
$g_c=$ Green circle
$r_r=$ Red rectangle
$y_s=$ Yellow square
$b_t-g_cr_r=y_s$
Isolating $g_c$
$b_t-y_s=g_cr_r$
$g_c=\frac{b_t-y_s}{r_r}$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.