simultaneous problem solving? year 10 extension work

eeek (Doh) these questions are confusing . year 10 extension work the teacher gave me.. need help. thank you

q.1an investor received $1400 interest per annum from a sum of money , with part of it invested at 10% and the remainder at 7% simple interest. This investor found that if she interchanged the amounts she had invested she could increase her return by $90 per annum. calculate the total amount invested.

q.2a tea wholesaler blends together three types of tea that normally sell for $10,$11,$12 per kilogram so as to obtain 100 kilograms f tea worth $11.20 per kilogram. If the same amounts of the two higher priced teas are used, calculate how much of each type must be used in the blend.