$x+x+x+x+x+x=$

$x\times x\times x\times x\times x=x^k$

The value of $k$ is _____.

$b\times b\times b\times b\times b\times b\times b=b^k$

The value of $k$ is _____.

$y÷z=y\times$_____

Write the base and the index of the power in $x^3$.

Write the base and the index of the power in $a^7$.

Write the base and the index of the power in $b^4$.

Write the base and the index of the power in ${\left(2y\right)}^5$.

For the algebraic expression $3x^2+5xy-7y^2+1$, what is the number of terms in the expression?