Rewrite one of the two equations above in the form ax+by=c, where a, b,c are constants, so that the sum of the new equations and the unchanged equations from the original system results in an equation in one variable

I would rewrite the second equation like this: multiply both sides by 4 to get

and then the sum of this rewritten one and the top row equation will be

which is an easy to solve equation with one variable (y)

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.

70

step-by-step explanation: