We have the translated equation:
0.23e + 0.11p = 1.70
Multiply throughout by 100
23e + 11p = 170, where e and p are positive integers.
Now, this is a problem in which we have an equation in 2 variables, but both variables can only take integer values.
Remember this rule: For such problems, there exists only one possible solution for each of the variables if the LCM of the coefficients of each variable + the lower coefficient is greater than the RHS of the equation. So in DS if this is violated, you cannot find a solution.
Manhattan's method to solve this problem is actually quite cool, I would recommend you understand it in case this pops up in a PS though that's unlikely.