You've not solved simultaneous equations before?

Two ways :

Elimination

5x - 3y - 8 = 0 ①
3x + 2y - 20 = 0 ②

① x 3 :
15x - 9y - 24 = 0 ③

② x 5 :
15x + 10y - 100 = 0 ④


④ - ③ :

15x + 10y - 100 - (15x - 9y - 24) = 0
19y - 76 = 0
19y = 76
y = 4


Sub y = 4 back into ①,

5x - 3(4) - 8 = 0
5x - 20 = 0
5x = 20

x = 4

Substitution

5x - 3y - 8 = 0 ①
5x = 3y + 8
x = 3/5 y + 8/5→ ③


3x + 2y - 20 = 0 ②


Sub ③ into ①,

3(3/5 y + 8/5) + 2y - 20 = 0

9/5 y + 24/5 + 2y - 20 = 0

19/5 y = 20 - 24/5 = 76/5

y = 76/5 × 5/19
= 4


x = 3/5 (4) + 8/5
= 12/5 + 8/5
= 20/5
= 4

I mistook "y" for "u" in the question and was wondering why "u" can be used to describe both a vector and a constant at the same time.

I suspect the student had thought that there were 3 variables in the two equations and therefore got stuck,

Surely she can read her own handwriting...


She takes this question from some online portal/platform anyway, so would have doubled checked the alphabets.