A vendor plans to sell mixed nuts for Php 20.00 per 50 grams with peanuts costing Php 1.50 per gram and Php 2.00 per gram for cashew. How many grams of each type should be mixed?

If I read your problem, you want to mix peanuts @1.50/gram with cashews @2.00/gram to have a mixture that sells for .40/gram. That ought to be a trick.