smc

The sequence $S_1,S_2,S_3,\cdots ,S_{10}$ has the property that every term beginning with the third is the sum of the previous two. That is, $$S_n=S_{n-2}+S_{n-1}\text{ for }n\ge 3.$$ Suppose that $S_9=110$ and $S_7=42$. What is $S_4$?