Solving two-step linear equations using addition and subtraction: ax+b=c

Lessons

1. Find x in the equation modelled by each diagram.
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2. Find x in the equation modelled by algebra tiles.
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3. Solve.
   1. $7x + 9 = 21$
   2. $98 - 2x = 14$
   3. $- 35 = 6x + 49$
   4. $- 4x - 11 = 109$
4. The total admission fee of an aquarium for 30 students is $240 after a group discount of $3 for each person. What is the original admission fee before the discount?