What is 200 millimetres equal to in centre meters?

What is the common difference in the following arithmetic sequence? 7,3,-1,-5

Beth makes batches of bluberry muffins and banna muffins. each batchis 6 muffins. she makes 2.5 batches of bluberry muffins. how many batches of bananna muffins should beth make if she wants to have a total of 60 muffins?

Atemperature of 1.64◦f corresponds to answer in units of ◦c.