chemistry
posted by eric .
A 141mg sample was placed on a watch glass that weighed 9.203 g. What is the weight of the watch glass and sample in grams?

9.203g watch glass mass
+0.141g sample mass

9.344 g total mass 
the sample weighs .141 grams. so in order to find the weight of the watch glass you will have to subtract the sample from the total weight(9.203g). Therefore, the watch glass weighs 9.062 grams.