Answer:
4 pieces
Step-by-step explanation:
This is because 3 add 1 makes 4 and 8 minus 4 makes 4
In the step after -6x+10=4x+20, he moved the terms incorrectly. you have to add 6x to both sides so it would be 10=4x+6x+20 which simplifies to 10=10x+20. subtract 20 from both sides to get -10=10x. divide both sides by 10. the answer is x=-1
You first work out the mean then for each number subtract the mean and square the result then work out the mean of those squared differences and take the square rot of that and you're done :)
