index.js

import React from 'react';
import ReactDOM from 'react-dom';

class Button extends React.Component {
    handleClick = () => {
        this.props.onClickFunction(this.props.incrementValue);
    }

    render() {
        return (
            <button onClick={this.handleClick}>
               +{this.props.incrementValue}
            </button>
        );
    }
}

const Result = (props) => {
  return (
      <div>{props.counter}</div>
  );  
};

class App extends React.Component {
    state = { counter: 0};

    incrementCounter = (incrementValue) => {
        this.setState((prevState) => {
            return {
                counter: prevState.counter + incrementValue
            }
        });
    }

    render () {
        return (
            <div>
                <Button incrementValue={1} onClickFunction={this.incrementCounter} />  
                <Button incrementValue={5} onClickFunction={this.incrementCounter} />
                <Button incrementValue={10} onClickFunction={this.incrementCounter} />
                <Result counter={this.state.counter}/>
            </div>
        );
    }
}

ReactDOM.render(<App />, document.getElementById('root'));