82 x 10 = 820

820 – 310 = 510

10 – 1.5 = 8.5

510 / 8.5 = 60

60 chairs

22 tables

Mr Lee bought a total of 82 tables and chairs altogether. He was given a discount of $10 per table and a discount of $1.50 per chair. He paid $310 less in all. How many tables did he buy?

EQ 1: Table + Chair = 82

EQ2: 10 Table + 1.5 chair = 310

EQ 3 = EQ1 * 10: 10 Table + 10 Chair = 820

EQ3 – EQ2: 8.5 chairs = 510

1 chair =  60

Tables: 82 – 60 = 22

82 x 1.50 = 123 (assume 82 chairs)
310 – 123 = 187 (discount amount : all tables more than all chairs)
10 – 1.50 = 8.50 (discount amount : 1 table more than 1 chair)
187/8.50 = 22 (number of tables)

Ans : 22 tables.