let age:number = 3; let isAdult:boolean = true; let a:number[] = [1,2,3]; let a2:Array = [1,2,3]; let week1:string[] = ['mon', 'tue', 'wed']; let week2:Array = ['mon', 'tue', 'wed']; let mrgintCtsfd:string | undefined = undefined; let nullableNumber:number | null = null; let color:'red' | 'orange' = 'red'; color = 'orange'; color = 'green'; // 에러 // yarn run tsc 시 오류된 부분 나옴 funtion sum( x:number..