Represent each marble by a 2-letter symbol: S=small, B=big, R=red, B=blue. First letter is the size.
Let N=total number of marbles=SR+SB+BR+BB=N.
BR=45,
SB+BB=3N/4,
SR/SB=2/3, SR=2SB/3,
SB=24+SR+BR=69+SR=69+2SB/3,
SB/3=69, SB=207, SR=2SB/3=138.
138+207+45+BB=N, N=BB+390.
207+BB=3N/4, 828+4BB=3N, N=(828+4BB)/3=BB+390,
828+4BB=3BB+1170, BB=1170-828=342,
N=BB+390=342+390=732.
Need to find 100(BR+BB)/N=100(45+342)/732=38700/732=52.87% approx.