Answer:
[tex] {eb}^{2} = {ab}^{2} + {ea}^{2} \\ {ab}^{2} = {eb}^{2} - {ea}^{2} \\ {ab}^{2} = {20}^{2} - {12}^{2} \\ ab = 16 \\ \\ {db}^{2} = {bc}^{2} + {dc}^{2} \\ {bc}^{2} = {db}^{2} - {dc}^{2} \\ {bc}^{2} = {20}^{2} - {16}^{2} \\ bc = 12 \\ \\ so \: ac = ab + bc \\ ac = 28[/tex]
