Question 1006345
Account for the materials.
x+y=3


Account for the cost of the order purchased.
(88/0.5)x+(213/0.1)y=1505


Slightly simplified, the system to solve, using x for quantity of L-Ribose and y for L-Gulose, is  {{{system(x+y=3,176x+2130y=1505)}}}.
The variables for x and y are in units of GRAMS as arranged here; not milligrams; but you could arrange differently if you preferred.