Can y’all help me on question 12?!

Select the correct answer from each drop-down menu. a system of equations and its solution are given below. system a complete the sentences to explain what steps were followed to obtain the system of equations below. system b to get system b, the equation in system a was replaced by the sum of that equation and times the equation. the solution to system b the same as the solution to system a.]

Which function represents the sequence? f(n)=n+3 f(n)=7n−4 f(n)=3n+7 f(n)=n+7

Cuántos triángulos forman un diamante