Question

Find two numbers a and b whose sum a + b is 4 and whose difference a − b is 8 .

Answer 1

see below

Explanation:

a + b = 4

a - b = 8 add the two equations to solve the system of equations

a + a + b + (- b) = 4 + 8

2a + 0b = 12

2a/2 = 12 /2

a = 6

a + b = 4

a - a + b = 4 -a

b = 4 - 6

b = -2