Simplify the expression. \( 7 a^{2}-15 a^{2}+18 a^{2} \) \( 7 a^{2}-15 a^{2}+18 a^{2}=\square \)

To simplify the expression \( 7 a^{2}-15 a^{2}+18 a^{2} \), you combine like terms. Start by adding and subtracting the coefficients: \[ 7 - 15 + 18 = -8 + 18 = 10. \] So, the simplified expression is: \[ 7 a^{2}-15 a^{2}+18 a^{2} = 10 a^{2}. \] Now, wasn't that a smooth ride through the land of coefficients?