The Pythagorean Theorem (image below)

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

The ratio of the measures of the three angles in a triangle is 2: 9: 4. find the measures of the angels

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?