Step by step
The question
Question: simplify 3(2x − 5).
Simplify means: write it shorter, with the same value.
3(2x − 5)
1 Open the brackets
The 3 in front of the bracket multiplies every part inside.
a(b + c) = ab + ac
So we write 3 times each part.
= 3(2x) + 3(−5)
Plus times minus is minus.
+ × − = −
3 times 2x is 6x.
3 times (−5) is −15.
= 6x − 15
2 Check
Let's check.
We pick a small number for each letter: x = 2.
Any number works, and a small one keeps the sums easy.
We put it into the question.
Question: 3 × (2 × 2 − 5) = 3 × (4 − 5)
= 3 × (−1) = −3
Now into our answer.
Answer: 6 × 2 − 15 = 12 − 15 = −3
Both give −3.
Same value, so 6x − 15 is right!
Both give −3
Let's look back.
First: open the brackets.
Last: check.
Answer
= 6x − 15