Someone please anwser at this point im sad and listening to nirvana​

How do you solve a question like this?

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

Which of these statements is correct? the system of linear equations 6x - 5y = 8 and 12x - 10y = 16 has no solution. the system of linear equations 7x + 2y = 6 and 14x + 4y = 16 has an infinite number of solutions. the system of linear equations 8x - 3y = 10 and 16x - 6y = 22 has no solution. the system of linear equations 9x + 6y = 14 and 18x + 12y = 26 has an infinite number of solutions.