Answer :

SoapyMcTavish
18) 
The Last case is 252 because 28 * 9 = 252. 
Second Case is 9 because 8*9 = 72, and 252 - 72 = 180, then you divide 180 over 20, and you get 9.
So, 28 * 9 = 20 * 9 + 8 * 9 = 252

19)
in Math, when they say "of", it means you need to multiply, so you get:
[tex] \frac{4}{7} * 98[/tex]
do it on the calculator and you get 56.

20)
To add fractions, they need to have the same denominator. Since here they got the same (10), you get:
[tex] \frac{6}{10} + \frac{1}{10} + \frac{4}{10} [/tex]
[tex] \frac{6+1+4}{10} [/tex]
[tex] \frac{11}{10} [/tex]

Hope this Helps! :D
18) [tex]\sf 28 * 9 = 20 * 9 + 8 * 9 = 252[/tex]

19) [tex]\sf \frac{4}{7} * 98[/tex]

[tex]\sf remember ~ that~98 ~can~also~be~written~as ~ \frac{98}{1} [/tex]

[tex]\sf \frac{4}{7} * \frac{98}{1} = \frac{4~*~98}{7~*~1} = \frac{392}{7} = 56[/tex]

20) [tex]\sf \frac{6}{10} + \frac{1}{10} + \frac{4}{10} = \frac{6~+~1~+~4}{10} = \frac{11}{10} = 1 \frac{1}{10} [/tex]

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