Find the value of x and classify the triangle

If the graphs of the linear equations in a system are parallel, what does that mean about the possible solution(s) of the system? a. there are infinitely many solutions. b. there is no solution. c. there is exactly one solution. d. the lines in a system cannot be parallel.

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?