how can I multiply two elements using typescript with react native?

I am working in a project with React Native and TypeScript. I have a TextInput that convert the Peso Argentino into Real Brasileiro, the currency value is fixed, I pretend to use an API later. However, when I put the value={this.state.coinValue} or onChangeText={coinValue => this.setState({ coinValue })} it returns me error in the state or props of the typescript. How can I solve this?

My current code:

interface Props {}interface State {    coinValue: number;}export class Exchange extends React.Component<Props, State> {    constructor(props: Props) {        super(props);        this.state = { coinValue: 0 };    }    currency = () => {        const real = 17.47;        const v = this.state.coinValue;        const result = v * real;        alert("$"+result+" Peso Argentino")    }    render() {        return(<View style={styles.container}><KeyboardAvoidingView                     style={styles.container}                     behavior={Platform.OS === "ios" ? "padding" : "height"}> <Header /><View style={styles.header}><Text style={styles.coin}>Moeda</Text><View style={styles.card}><Image                                     style={styles.img}                                    source={arFlag}                                /><Text style={styles.typeOfCoin}>Peso Argentino</Text><Text style={styles.valueOfCoin}>R$17,28</Text><Feather                                     name="rotate-ccw"                                    size={14}                                    color={colors.heading}                                    /></View></View><View style={styles.value}><Text style={styles.insertValue}>Insira o valor</Text><TextInput                                 style={styles.input}                                placeholder="9000"                            />    <View style={styles.btn}><Button                                     title="Converter"                                /></View></View><View style={styles.convertedValue}>                            {/** <Text style={visible ? styles.unhideValue : styles.hideValue}>{ newValue }</Text>*/}<Text style={[styles.textValue}>R$10M</Text></View></KeyboardAvoidingView></View>        );    }}