The sum of two numbers is =21.five times the first number is added to two times the second number is =66 what the number

Answer 1

Eq1: x + y = 21.
Eq2: 5x + 2y = 66.
Multiply Eq1 by (-)5 and add the Eqs:
-5x - 5y = -105
+5x + 2y = +66.
Sum: -3y = -39
Y = 13.

In Eq1, replace Y with 13 and solve for X:
x + 13 = 21.
X = 8.

Answer 2

How do the get -105 and sum of -3y=39

Answer 3

11 and 10, and please explian well i do not understand

Answer 4

Let the numbers be x and y.
If x + y = 21, y = 21 - x
five times the first number x = 5 x x = 5x
two times the second number y = 2y where y is 21 - x = 2(21-x)

Solution
5x + 2(21-x) =66
5x + 42 - 2x = 66
bring like terms together
5x - 2x = 66 - 42
3x = 24
x = 24/3
x = 8
y = 21 - 8 = 13

Therefore, the two numbers are 8 and 13.