Help it’s due soon!! Are the triangles similar?

Can someone me out here and the tell me the greatest common factor

Mat bought a phone for $100. he has to pay $30 per mouth. if he has paid $640 in total, how many mouth has he had the phone?

Your friend uses c=50p to find the total cost, c, for the people, p, entering a local amusement park what is the unit rate and what does it represent in the context of the situation?