How do I solve this problem?

(2t/5) + (t/7) = 57
(14t/35) + (5t/35) = 57
(14t+5t)/35 = 57
19t = 57*35
19t = 1995
t = 1995/19
t = 105

Second one:

1/7x - 4/7 = 2/7
x/7 - 4/7 = 2/7
(x-4)/7 = 2/7
x-4 = 2
x = 6

1)
2t/5 + t/7 = 57
14t/35 + 5t/35 = 57
19t = 35(57)
t = 1995/19
t = 105

2)
1/7x - 4/7 = 2/7
1/7x = 2/7 + 4/7
1/7x = 6/7
7/7x = 6
7 = 42x
x = 7/42
x = 1/6

1) 2t/5 + t/7 = 57

Multiply everything by the LCM of the denominators to eliminate them (in this case, 35)

14t + 5t = 1995
19t = 1995
t = 105

2) Same thing, but the LCM here is 7x:

1/(7x) - 4/7 = 2/7
1 - 4x = 2x
1 = 6x
x = 1/6

1) 2t/5 + t/7 = 57

find a common denominator which is 35:

14t/35 + 5t/35 = 1995/35

multiply everything by 35:

14t + 5t = 1995
19t = 1995
t = 105

2. They already have common denominators, so multiply everything by 7:

x - 4 = 2
x = 6