Severity: Warning

Message: count(): Parameter must be an array or an object that implements Countable

Filename: controllers/calculator.php

Line Number: 37

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Here the unknown variable is x

Any operation that is performed should be done on both sides of the equation.

Step 1: Add -7 on both sides of the given equation

2x + 7 – 7 = 15 – 7

2x = 8

Step 2: Divide by 2 on both sides of the given equation

2x / 2 = 8 / 2

x = 4

CHECK: 2x + 7 = 15

2(4) + 7 = 15

8 + 7 = 15

15 = 15

Hence the result is x= 4

Here there are two unknown variables x and y

x + y = 24 => y = 24 – x

Substitute y = 24 – x in the second equation 2x – y = 3

2x – (24 – x) = 3

2x – 24 + x = 3

3x – 24 = 3

3x = 27

x = 9

Substitute x = 9 in the equation y = 24 – x

y = 24 – 9

y = 15

Solution set is (9, 15)

x + y = 24

2x – y = 3

3x = 27

x = 9

Substitute x = 9 in x + y = 24

9 + y = 24

y = 24 – 9

y = 15

Solution set is (9, 15)