Idon't understand the system of equations

Lisa has three classes that each last 50 minutes. what is the total number of minutes of the three classes

Apolynomial has two terms. check all of the factoring methods that should be considered. common factor difference of cubes sum of cubes difference of squares perfect-square trinomial factoring by grouping

This summer the number of tourists in salem increased 4.5% from last years total of 426000. how many more tourists came to salem this summer