Exercises
1. the sum of both numbers of a number is 14. on having exchanged the numbers of the tens with that of the units, the number increases in 18. it finds the original number.
2. the sum of two numbers is 21 and his difference is 5. ¿which are the numbers?
i am grateful for them to him very much indeed : )

Compare these two waves: the blue and orange waves have the same pitch, but the blue wave is louder. the blue and orange waves have the same volume, but the blue wave has a higher pitch. the orange wave has a higher pitch, but the blue wave is louder. the blue wave has a higher pitch, but the orange wave is louder.

International calls require the use of a country code. many country codes a 3-digit numbers. country codes do not begin with a 0 or 1. there are no restrictions on the second and third digits. how many different 3-digit country codes are possible?

If the value of x increases by 5, how does the value of m(x + 3) change? a) it increases by 5m. b) it increases by 8m. c) it decreases by 5m. d) it decreases by 8m.