Which statement about the following argument is true? argument: if it snows, the roads will get slippery. it's snowing. therefore, the roads are slippery. a: the argument is valid by the law of syllogism. b: the argument is valid by the law of detachment. c: the argument is invalid. d: the argument is valid but does not follow the law of syllogism or the law of detachment.

The students at jefferson middle school are raising money for a charity by selling t-shirts and hats. the number of t-shirts sold was 3 times the number of hats. the profit was $5 for each t-shirt sold and $2.50 for each hat sold. the students raised $840 for the charity. they used the system below to analyze their success and found the solution to be (144, 48). 5x+2.50y=840 x=3y how much did they earn from t-shirt sales?