4x + 3y = 17 and 5x – 3y = 1
–5m + 6n = –8 and –5m + 8n = 6
2x – 7y = –9 and 6x + 7y = 57
5p – 4q = 3 and –5p – 4q = 13
6c + d = 12 and c – d = 2

Equation:4x+3y=17

x=-3/4y+17/4

y=-4/3x+17/3

Equation:5x-3y=1

x=3/5y+1/5

y=5/3x+-1/3

Equation:–5m + 6n = –8

m=6/5n+8/5

n=5/6m+-4/3

Equation:–5m + 8n = 6

m=8/5n+-6/5

n=5/8m+3/4

Equation:2x – 7y = –9

x=7/2y+-9/2

y=2/7x+9/7

Equation:6x + 7y = 57

x=-7/6y+19/2

y=-6/7x+57/7

Equation:5p – 4q = 3

p=4/5q+3/5

q=5/4p+-3/4

Equation:–5p – 4q = 13

p=-4/5q+-13/5

q=-5/4p+-13/4

Equation:6c + d = 12

c=-1/6d+2

d=-6c+12

Equation: c – d = 2

c=d+2

d=c-2

8 hours

Step-by-step explanation:

t = time for Bob and Nina to make 60 leashes

Bob = 7 in 2 hr  = 3.5 in 1 hr

Nina = 4 in 1 hr

3.5 + 4 = 7.5 leashes per hour

t = 60/7.5 = 8 hours