Which of the following best defines a mixture problem in algebra?

You read: "A baker uses two blends of flour to make 100 pounds of dough." Which sketch and variable assignment best represents the mixture before writing equations?

Which equation correctly models the following situation: $x$ liters of 6% saline mixed with $y$ liters of 14% saline creating a 10 liter solution of 9% saline?

A jar contains nickels and dimes totaling \$1.25. There are twice as many dimes as nickels. How many of each coin are in the jar?

Three different sugar syrups (A, B, C) are to be combined, but only the total mass and overall concentration are specified. If the concentrations of A, B, and C are 5%, 10%, and 20% respectively, and the total mass is M, explain why you cannot uniquely determine all three masses from only the total mass and overall percentage, and give an expression showing one variable in terms of the other two.