Answer:
Lily can invite 8 friends ,
10 times 8 equals 80
80 plus 45 equals 125
Step-by-step explanation:
<h3>Answer:</h3>
x=5, y=2
<h3>Explanation:</h3>
The second equation gives an expression for x that can be substituted into the first equation.
... (y+3) +y = 7 . . . . . .substitute y+3 for x
... 2y + 3 = 7 . . . . . . . colect terms
... 2y = 4 . . . . . . . . . . subtract 3 from both sides
... y = 2 . . . . . . . . . . . . divide both sides by 2
Using the expression for x, we can find its value.
... x = y + 3
... x = 2 + 3 . . . . . . . . . substitute for y
... x = 5
The solution is (x, y) = (5, 2).
Answer:
The three numbers are 56/5, -39/5 and 78/5.
Step-by-step explanation:
EQUATION 1:
First number: x
Second number: y
Third number: z
x + y + z = 19
EQUATION 2:
Sum of following is 77
Twice the first number: 2x
5 times the second number: 5y
6 times the third number: 6z
So, 2x + 5y + 6z = 77
EQUATION 3:
Difference between first and second number is 19.
x - y = 19
Equation 1: x + y + z = 19
Equation 2: 2x + 5y + 6z = 77
Equation 3: x - y = 19
1. Find x in terms of y
x - y = 19
x = 19 + y
2. Find y in terms of z by putting the value of x in first and second equation
x + y + z = 19
(19 + y)+ y + z = 19
2y + z = 19 - 19
2y + z = 0
y = -z/2
and
2(19+y)+5y+6z=77
now putting the value of y in this equation
2(19-z/2)+5(-z/2)+6z=77
38 - z -5z/2 +6z = 77
5z/2 + 38 = 77
5z/2 = 39
z = 78/5
Now, y = -z/2
y = (-78/5)/2
y = -39/5
and x = 19 + y
x = 19 - 39/5
x = 56/5
Therefore, the three numbers are 56/5, -39/5 and 78/5.
Keyword: Sum
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