Browse · MATH Print → jmc algebra junior Problem Given ab+bc+cd+da=30 and b+d=5, find a+c. Solution — click to reveal Write ab+bc+cd+da=(a+c)b+(c+a)d=(a+c)(b+d), so a+c=b+dab+bc+cd+da=530=6. Final answer 6 ← Previous problem Next problem →