Find the sum of the like terms $18ab,5ab,12ab$.

Subtract the first term from the second term in $2xy,7xy$

If we subtract the first term from the second term in $5a^2,10a^2$ we get $k{a}^2$, then find the value of $k$.

Subtract the first term from the second term in $12y,3y$

If we subtract the first term from the second term in $6x^{2}y,4x^{2}y$ we get, $k{x}^{2}y$, then find the value of $k$.

Subtract the first term from the second term in $6xy,-12xy$