[ruslan_mart]

1.

var a = ['first', 'second', 'third', 'fourth', 'fifth', 'sixth', 'seventh', 'eighth', 'ninth', 'tenth'],
    b = 'sixth',
    result = a.indexOf(b);

alert(result);

2.

var a = [2, 6, 9, 4, 0, 2, 3, 5, 7, 9];

a = a.map(function(n, i) {
    return n + i;
});

alert(a);

3.

var a = [2, 6, 9, 4, 0, 2, 3, 5, 7, 9],
    max = Math.max.apply(Math, a),
    min = Math.min.apply(Math, a);

alert('Max: ' + max + '\nMin: ' + min);