Question

1.The houses are small so they are cheap
=> the smaller
2.To do morning exercise regularly is good for your health         HEALTH
=>
3.Ha had a toothache yesterday.We had a toothache yesterday      SO
=>

Answer 1

1 the houses are, the cheaper they are.

2  It's good for your health to do morning exercise regularly.

3  Ha had a toothache yesterday and  so did we.