What's the difference between er & ir verbs in the preterite tense in spanish?

Achemist mixes 4 liters of one acid solution with 10 liters of a 40% solution, resulting in a 30% acid solution. what is the value of x, the acid concentration of the first solution

Which verb correctly completes the sentence? carolina cansada porque paseó por el parque todo el día. a. está b. es c. estoy d. soy

Scenario 2: you are asked to write a short paragraph in spanish. what is the best way to complete the assignment while keeping your integrity? how will you find and use the information from the lesson? what should you be careful about while writing your paragraph and what are some things you should avoid?