In January, a few foreign pupils were enrolled into the P5 classes.<br>As a result, the number of P5 boys increased by 10% to 121 and the number of P5 girls increased by 4% to 156. <hr> Find the number of P5 boys at first. <br> <input min="0" type="number" id ="imp6pg111q5b_1" class="lineinput" placeholder="?" />