Basic Equations - Difficult (for scores form 600 to 800)
STRATEGY: Read the question two or three times to be
sure you understand what it says.
| STRATEGY: Write all the steps to avoid careless errors.
(a + b) (a - b) = 99
If (a + b) = 11, substitute 11 for (a + b):
11 (a - b) = 99
(a - b) = 9
STRATEGY: Read the question again to be sure you know what it asks.
If (a + b) = 11 and (a - b) = 9, solve for x using simultaneous equations:
(a + b) = 11
+ (a - b) = 9
2a = 20
a = 10
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