tolongin aku dong... ini kepepet banget

Jawabannya adalah:
13. A
14. C. 

13) ( 2 / x ) - ( 1 / y ) = 2

2(y) - 1 ( x )
----------------- = 2
x • y

2y - x = 2( xy )

2y - x = 2xy .... pers 1

( 3 / x ) - ( 4 / y ) = 18

3 ( y ) - 4 ( x )
-------------------- = 18
x • y

3y - 4x = 18 ( xy )

3y - 4x = 18xy .. pers 2

pers 1 & 2
2y - x = 2xy |×4
3y - 4x = 18xy
maka
8y - 4x = 8xy
3y - 4x = 18xy
------------------(-)
5y = - 10xy
x = 5y / - 10y
x = - ½

subtitusi ke pers
2y - x = 2xy
2y + ½ = 2(-½)y
2y + ½ = - y
2y + y = - ½
3y = - ½
y = - ½ ÷ 3
y = - ½ × 1/3
y = - 1/6

hp = ( - ½ , - 1/6 ) ( A )

14) ½x + y = 2½
½x + y = 5/2 ( dikali 2)
x + 2y = 5 ... pers 1

pers 1 & 2
3x - 4y = 5
x + 2y = 5 |×2
maka
3x - 4y = 5
2x + 4y = 10
-------------------(+)
5x = 15
x = 3

subtitusi ke pers
x + 2y = 5
3 + 2y = 5
2y = 5 - 3
2y = 2
y = 1

nilai
x = p = 3
y = q = 1
p + q = 3 + 1 = 4 ( C )