The system of linear equations represents the situation is;
x + y = 125
x + y = 1255x + 8y = 775
<h3>Simultaneous equation</h3>
Simultaneous equation is an equation in two unknown values are being solved for at the same time.
let
- number of quick washes = x
- number of premium washes = y
x + y = 125
5x + 8y = 775
From equation (1)
x = 125 - y
5x + 8y = 775
5(125 - y) + 8y = 775
625 - 5y + 8y = 775
- 5y + 8y = 775 - 625
3y = 150
y = 150/3
y = 50
x + y = 125
x + 50 = 125
x = 125 - 50
x = 75
Therefore, the number of quick washes and premium washes Monica’s school band had is 75 and 50 respectively.
Learn more about simultaneous equation:
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First off, let's convert the percentages to decimal format, so our 77% turns to 77/100 or 0.77, and our 55% turns to 55/100 or 0.55 and so on
now, the sum of both salines, must add up to the 77% mixture, let's say is "y"
so, 11 + 4 = y, and whatever the concentration level is, must also sum up to the mixture's concentration of 77%
anyway thus

solve for "x"
Answer:
x=9
Step-by-step explanation:
7x-11 = 4x-2
7x-4x=11-2
3x=9
x=9
Since he sold it for $75 more,
% Mark Up = Mark Up/ Cost Price x 100%
% Mark Up = 75 / 125 x 100% = 0.6 x 100% = 60%
Percent Mark Up = 60%
Hope this helps :)