On serena's tenth birthday, her mom was 3 times serena's age. how old will serena and her mom be when here mom's age times 0.5 will equal serena's age? (i think there is a typo in my book. if so, i think this is the question they meant to ask/type. how old will serena and her mom be when serena's ages times 0.5 equals her mom's age? basically, a x 0.5 = b)