1.) An investor wishes to realize a return of 12% on a total of two investments. If he has $10,000 invested at 10%, how much additional money should be invested at 16%?

2.) A woman invested $25000 in two business ventures. Last year she made a profit of 15% from the first venture but lost 5% from the second venture. If last year's income from the two investments was equivalent to a return of 8% on the entire amount invested, how much had she invested in each venture?

Can you show me how it's done? I have the answers, I just don't know how to solve it. Thanks!