Final answer:
To find the total number of train cars Alejandro and Jess have, multiply the number of sets each person owns by the number of cars in each set and then add the two totals together.
Step-by-step explanation:
To find the total number of train cars Alejandro and Jess have, we need to add the number of cars in Alejandro's sets to the number of cars in Jess's sets. Alejandro has 3 sets of trains, and each set has 18 cars. So, Alejandro has a total of 3 x 18 = 54 train cars. Jess has 2 sets of trains, and each set has 18 cars. So, Jess has a total of 2 x 18 = 36 train cars. To find the total number of train cars they have, we add Alejandro's total to Jess's total: 54 + 36 = 90 train cars.
Learn more about addition of numbers