SimpleCalculator.html

<template>
  <lightning-card title="SFDCFacts Calculator" icon-name="standard:formula">
    <lightning-layout multiple-rows="true">
      <lightning-layout-item size="12" padding="around-small">
        <lightning-input type="number" label="First Number" name="firstName" onchange={onNumberChange}></lightning-input>
      </lightning-layout-item>
      <lightning-layout-item size="12" padding="around-small">
        <lightning-input type="number" label="Second Number" name="secondName" onchange={onNumberChange}></lightning-input>
      </lightning-layout-item>
      <lightning-layout-item size="12" padding="around-small">
        <lightning-button-group>
          <lightning-button label="Add" icon-position="right" icon-name="utility:add" onclick={onAdd}></lightning-button>
          <lightning-button label="Subtract" icon-position="right" icon-name="utility:dash" onclick={onSub}></lightning-button>
          <lightning-button label="Multiply" icon-position="right" icon-name="utility:close" onclick={onMultiply}></lightning-button>
          <lightning-button label="Divide" icon-position="right" icon-name="utility:magicwand" onclick={onDivide}></lightning-button>
        </lightning-button-group>
      </lightning-layout-item>
      <lightning-layout-item size="12" padding="around-small">
          <p class="slds-m-top_medium" style="color:blue; font-weight:bold;">{result}</p>
      </lightning-layout-item>
    </lightning-layout>
  </lightning-card>
</template>