Arithmetic Grade Six

Lesson One Hundred Sixty-three: Variables

Sometimes a single missing number problem can involve both multiplication and addition or subtraction. Also sometimes we are given the missing number and asked to find the answer to the equation. Here's an example: 


  if x = 7, then what does 2x + 2 equal?
To solve this problem we substitute 7 for x (the slot where the missing number goes) and then solve the problem: 

  	2 * 7 + 2 = 16
Here are a few more examples: 

	if y = 8, then what does 3y - 3 equal?
           SOLUTION:  3 * 8 - 3 = 21

	if n = 3, then what does 4n + 5 equal?
	   SOLUTION:  4 * 3 + 5 = 17

	if z = 2, then what does 3n - 5 equal?
	   SOLUTION:  3 * 2 - 5 = 1
In each case all you have to do is substitute the value for the letter and then just solve the problem as usual. Here are a few more examples presented in tabular form:
value of xequation: 4x - 2
414
310
518
726

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