Substitution?

Question

3a-5b=10
a+7b=12

thats the problem can you please explain how i would use the substitution method.
I know I need to take one of those and solve for either a or b. but i get lost somehow :(

Answer 1

a = 12 - 7b

3(12 - 7b) - 5b = 10
36 - 21b - 5b = 10
- 26 b = - 26
b = 1

a + 7 = 12
a = 5

a = 5 , b = 1

Answer 2

this is a simultaneous eqn.

u can solve any of them first

a=12-7b

then in the first equation
3(12-7b)-5b=10
36-21b-5b=10
-26b=-26
b=1
a=5

Answer 3

a=12-7b

then in the first equation
3(12-7b)-5b=10
36-21b-5b=10
-26b=-26
b=1
a=5

Answer 4

3*( 12-7b) - 5b = 10

get b , then get a

Answer 5

3a-5b=10--------(1)
a+7b=12
or a=12-7b-------(2)
Subsituting (2) in (1),we get
3(12-7b)-5b=10
or 36-21b-5b=10
or -26b=-26
or b=1,subsituting in (1),we get
3a-5X1=10
or 3a=15
or a=5 ans