1. a number increased by 21 is 28. find the number

2. a number decreased by 12 is equal to 30. find the number.

3. 8 less than a number is 15. fid the number

See my previous answer to this question.

http://www.jiskha.com/display.cgi?id=1234058590

can you help me solve this answer and explain it to me.

twice a number plus 7 equal 9

twice a number plus 7 equals 9

To find the answers to these problems, we can use algebraic equations. Let's go through each question step by step:

1. Let's call the unknown number "x". The problem states that when you increase this number by 21, it becomes 28. So we can write it as an equation: x + 21 = 28. To solve for x, we need to isolate it on one side of the equation.

We can do this by subtracting 21 from both sides:
(x + 21) - 21 = 28 - 21.
This simplifies to:
x = 7.
So the number is 7.

2. Let's call the unknown number "x" again. The problem states that when you decrease this number by 12, it becomes 30. So we can write it as an equation: x - 12 = 30. To solve for x, we need to isolate it on one side of the equation.

We can do this by adding 12 to both sides:
(x - 12) + 12 = 30 + 12.
This simplifies to:
x = 42.
So the number is 42.

3. Let's call the unknown number "x" once more. The problem states that when you subtract 8 from this number, it becomes 15. So we can write it as an equation: x - 8 = 15. To solve for x, we need to isolate it on one side of the equation.

We can do this by adding 8 to both sides:
(x - 8) + 8 = 15 + 8.
This simplifies to:
x = 23.
So the number is 23.

By using algebraic equations, we can easily solve these types of problems.