(13 2/5 + 7 2/3)-(6 2/3 - 3/5)
13 2/5+7 2/3=67/5+23/3=201+115/15=316/15 6 2/3-3/5=20/3-3/5=100-9/15=91/15 316/15-91/15=316-91/15=225/15=15