JavaScript Inputs Calculating

Inputs Calculating

<INPUT TYPE=text NAME="firstNumber"  SIZE=3 MAXLENGTH=3>
<INPUT TYPE=text NAME="secondNumber" SIZE=3 MAXLENGTH=3><br>
<INPUT TYPE=button NAME="Addition" VALUE="+"   width=20 onClick="Answer.value=(eval(firstNumber.value) + eval(secondNumber.value));">
<INPUT TYPE=text NAME="Answer">
</form>