Rearrange the first equation
2x + y = 20
take away 2x from both sides
y = 20 - 2x
substitute this y value into the second equation
6x - 5(20 - 2x) = 12
6x -100 +10x = 12
add 100 to both sides
6x + 10x = 112
16x = 112
divide both sides by 16
x = 7
Substitute this x value into the first equation to get y.
2(7) + y = 20
14 + y = 20
take away 14 from both sides
y = 6
So, y = 6 and x = 7
A1=6*1-12=-6 arithmetic sequence
a14=6*14-12=72
sum =n(a(1)+a(n))/2
sum =14*(-6+72)/2=462
72kg - 54kg
180kg - xkg
cross multiply
72 · x = 180 · 54
72x = 9720 |divide both sides by 72
x = 135
Answer: 135kg.
