54 i believe
explanation: if you put 18 crayons in 3 baskets each it’s gotta b 54
let's convert firstly the mixed fractions to improper fractions and then add up.
![\bf \stackrel{mixed}{2\frac{3}{8}}\implies \cfrac{2\cdot 8+3}{8}\implies \stackrel{improper}{\cfrac{19}{8}}~\hfill \stackrel{mixed}{1\frac{1}{4}}\implies \cfrac{1\cdot 4+1}{4}\implies \stackrel{improper}{\cfrac{5}{4}} \\\\\\ \stackrel{mixed}{2\frac{7}{8}}\implies \cfrac{2\cdot 8+7}{8}\implies \stackrel{improper}{\cfrac{23}{8}} \\\\[-0.35em] ~\dotfill](https://tex.z-dn.net/?f=%5Cbf%20%5Cstackrel%7Bmixed%7D%7B2%5Cfrac%7B3%7D%7B8%7D%7D%5Cimplies%20%5Ccfrac%7B2%5Ccdot%208%2B3%7D%7B8%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B19%7D%7B8%7D%7D~%5Chfill%20%5Cstackrel%7Bmixed%7D%7B1%5Cfrac%7B1%7D%7B4%7D%7D%5Cimplies%20%5Ccfrac%7B1%5Ccdot%204%2B1%7D%7B4%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B5%7D%7B4%7D%7D%20%5C%5C%5C%5C%5C%5C%20%5Cstackrel%7Bmixed%7D%7B2%5Cfrac%7B7%7D%7B8%7D%7D%5Cimplies%20%5Ccfrac%7B2%5Ccdot%208%2B7%7D%7B8%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B23%7D%7B8%7D%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill)

Your mistake is that 1 pound and 15 ounces <em>does not equal</em> 1.15 pounds. You also did not make everything into the same measurement (you mixed up pounds and ounces). I will make everything into the measurement of <em>ounces</em>, since the numbers do not come out clean if we do pounds.
18 pounds (original) = 288
1 pound 15 ounces = 31 ounces
3 1/8 pound = 50 ounces
4 1/2 pound = 72 ounces
So after cutting out those steaks, Mr. Rand has 288-31-50-72 = 135 ounces. Then, it states that he divides those up into 9 ounce patties:
135/9 = 15 patties
And sells them at 3 for $3.12. There are 5 3's in 15 patties, so it is 5 * $3.12 = Mr Rand receives $15.60 for the patties.
3x+ 8= x-4
2x + 8= -4
2x= -12
x= -6