App.js

import { StatusBar } from 'expo-status-bar'
import React from 'react'
import { StyleSheet, Text, View, Button, TextInput } from 'react-native'

export default function App() {
  const [result, setResult] = React.useState(0)

  const [num1, setNum1] = React.useState('')

  const [num2, setNum2] = React.useState('')

  const addition = () => {
    const sum = parseFloat(num1) + parseFloat(num2)
    setResult(sum)
    setNum1('')
    setNum2('')
  }

  const subtraction = () => {
    const sub = parseFloat(num1) - parseFloat(num2)
    setResult(sub)
    setNum1('')
    setNum2('')
  }

  return (
    <View style={styles.container}>
      <View style={styles.container}>
        <Text style={{ fontSize: 18 }}>Result = {result}</Text>
        <TextInput
          style={{ width: 200, borderColor: 'gray', borderWidth: 1 }}
          value={num1}
          onChangeText={(text) => setNum1(text)}
          keyboardType="numeric"
        />
        <TextInput
          style={{ width: 200, borderColor: 'gray', borderWidth: 1 }}
          value={num2}
          onChangeText={(text) => setNum2(text)}
          keyboardType="numeric"
        />
      </View>
      <View style={styles.buttonContainer}>
        <Button title=" + " onPress={addition} />
        <Button title=" - " onPress={subtraction} />
        <StatusBar style="auto" />
      </View>
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    flex: 2,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
  buttonContainer: {
    flex: 5,
    width: 80,
    flexDirection: 'row',
    backgroundColor: '#fff',
    alignItems: 'flex-start',
    justifyContent: 'space-around',
  },
})