Lisa arranged 66 roses in 7 vases some vases had 6 red roses and the others had 12 pink roses how many vases had red roses?

Let ( r ) be the number of vases with red roses and ( p ) be the number of vases with pink roses. We know that ( r + p = 7 ) and the total number of roses is ( 6r + 12p = 66 ). Solving these equations, we first simplify the second equation to ( r + 2p = 11 ). Substituting ( p = 7 - r ) into this gives ( r + 2(7 - r) = 11 ), leading to ( r = 5 ). Thus, there are 5 vases with red roses.