B + 12.5x = 400, where b is the base salary and x is the amount of subscriptions he needs to sell.
let's firstly convert the mixed fractions to improper fractions and then add them up.
![\bf \stackrel{mixed}{36\frac{4}{9}}\implies \cfrac{36\cdot 9+4}{9}\implies \stackrel{improper}{\cfrac{329}{9}} \\\\\\ \stackrel{mixed}{10\frac{2}{9}}\implies \cfrac{10\cdot 9+2}{9}\implies \stackrel{improper}{\cfrac{92}{9}}~\hfill \stackrel{mixed}{18\frac{2}{9}}\implies \cfrac{18\cdot 9+2}{9}\implies \stackrel{improper}{\cfrac{164}{9}} \\\\[-0.35em] ~\dotfill](https://tex.z-dn.net/?f=%5Cbf%20%5Cstackrel%7Bmixed%7D%7B36%5Cfrac%7B4%7D%7B9%7D%7D%5Cimplies%20%5Ccfrac%7B36%5Ccdot%209%2B4%7D%7B9%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B329%7D%7B9%7D%7D%20%5C%5C%5C%5C%5C%5C%20%5Cstackrel%7Bmixed%7D%7B10%5Cfrac%7B2%7D%7B9%7D%7D%5Cimplies%20%5Ccfrac%7B10%5Ccdot%209%2B2%7D%7B9%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B92%7D%7B9%7D%7D~%5Chfill%20%5Cstackrel%7Bmixed%7D%7B18%5Cfrac%7B2%7D%7B9%7D%7D%5Cimplies%20%5Ccfrac%7B18%5Ccdot%209%2B2%7D%7B9%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B164%7D%7B9%7D%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill)

We'll get started on that as soon as you share the whole
table of other information that goes with that question.
A parallelogram has 4 sides. there are different Parallelograms to know but what you asked was a Square. A square is a parallelogram that has all angles at 90° and Congruent to each other