Explanation:
0.05 = 2a + 5b
0.2 = 8a + 2b
the trick is to multiply the equations with contacts, so that an addition or subtraction of the equating can be made, and one variable is eliminated in that result, which allows us then to solve for the second variable.
and then we use one of the original equations to solve for the first variable.
in our case, multiplying the first one by 4 and then subtracting the second one sends to be the simplest approach :
0.2 = 8a + 20b
- 0.2 = 8a + 2b
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0 = 0 + 18b
b = 0/18 = 0
0.05 = 2a + 5b = 2a + 5×0 = 2a
a = 0.05 / 2 = 0.025
a = 0.025
b = 0