The string would have to be 4 feet long to have a frequency of 400cps because each foot=100cps
Answer and explanation:
They are not equivalent because if we simplify the second expression, the result isn't the same:
7(y×b)+3b
= 7(yb)+3b
=7yb + 3b
Therefore 7yb+3b≠7y+7b+3y
And even though you meant
7(y+b)+3b
=7y+7b+3b
=7y+10b
7y+10b≠10y+7b
That prob means you got it wrong, unless your teacher told you that there could be a decimal