get values from an array

I have been searching for a few hours now and I can’t find what I’m looking for.
Mabye I’m searching for the wrong thing but I hope someone can help me.

I’m making an Iphone app ( my first one ) and I created an array:

NSMutableArray *first = [[NSMutableArray alloc] initWithCapacity: 3];
[first insertObject: [NSArray arrayWithObjects: @“1.700”, @“1.425”, @“1.825”, nil] atIndex: 0];
[first insertObject: [NSArray arrayWithObjects: @“1.750”, @“1.475”, @“1.875”, nil] atIndex: 1];

The next thing i need is to get the all of the values where the first value is “1.700”, and show the all in a label.

How can I get this done? Please help me, or at least point me in the right direction. I realy want to learn this…

So, to clarify, you want to return all the items of array “first” where a sub-array contains “1.700”?
How are you making all the items for array “first”? Are you manually making all those objects? Or will it be procedural later on?
I would say that you have to loop through every item of array “first”, and then in each of those items, loop through all the values in the sub-array. If the item is found, then you have some other array where you either add an integer that corresponds to the index of “first”, or do something else to … well whatever needs done then.