John has 12 marbles. Sandra has 10 more marbles than Kathy. Kathy has 4 times as many marbles as John. How many marbles does Sandra have?

This question asks how students can formulate linear equations from worded questions. 

The first step is to give each person an algabraic symbol. j for John, s for Sandra and k for Kathy works fine. 

Next, students shoud identify key words in the question that translate in to mathematical symbols. In this case, 'has' means '=', 'more than' means '+' and 'times as many as' means 'x'. 

Students should create 3 equations. The first should be J = 12. The next is S = 10 + K. The next is K = 4 x J. 

Students should then subsititue J in to K = 4 x J and then substitute that answer in to S = 10 + K in order to find S. 

The final answer should be 58 marbles.