To compare the two, you either have to convert both to decimals or both to fractions.
To convert 0.7 to a fraction, remember that 0.7 is 7/10. To compare 7/10 to 3/5, they must have the same denominator. 3/5 * 2/2 (since 2/2 is basically 1 and anything times 1 equals itself) = 6/10. Since 7/10 > 6/10, 0.7 is greater.
To convert 3/5 to a decimal, remember that 3/5 = 6/10 (what we did in the last part). 6/10 = 0.6. Since 0.7 > 0.6, that means 0.7 is greater than 3/5.
