$\text{1.}$ No, they didn't.
$\text{→}$ Last Sunday Tom and Mary stayed at home.
$\text{2.}$ No, they didn't.
$\text{→}$ They helped their parents.
$\text{3.}$ They helped their parents.
$\text{4.}$ They were working in the garden.
$\text{→}$ When the teacher came, they were working in the garden.
$\text{5.}$ They were having their parents when the teacher came.
$\text{→}$ Tom was helping his father and Mary was helping her mother.
$\text{6.}$ No, he wasn't.
$\text{7.}$ He was helping his father.
$\text{8.}$ Mary was helping their mother.
$\text{9.}$ Yes, they were.
$\text{→}$ They were tired.
$\text{10.}$ Yes, they were.
$\text{→}$ They were tired, but they were happy.