Question

2x/5+3y/9=10
2x/5-3y/9=5
By substituting method
​

Answer 1

Answer:

$\frac{2x}{5} + \frac{3y}{9} = 10 \\ \frac{18x + 15y}{45} = 10 \\ 18x + 15y = 10 \times 45 \\ 18x + 15y = 450⟹⓵ \\ \\ \frac{2x}{5} - \frac{3y}{9} = 5 \\ \frac{18x - 15y}{45} = 5 \\ 18x - 15y = 5 \times 45 \\ 18x - 15y = 225⟹⓶ \\ \\ 18x + 15y= 450 \\ 18x - 15y = 225 \\ - - - - - - - - - \\ 36x = 675 \\ x = \frac{ \cancel{ 675} _{ \: \: \: 225}}{ \cancel{ 36} _{ \: \: \: 12}} \\ x = \frac{ \cancel{ 225} _{ _{ \: \: \: 75}} }{ \cancel{ 12} _{ \: \: \: 4} } \\ \boxed{ \large x = \underline{ \underline{ \bf \frac{75}{4} }}} \\ \\ 18x + 15y = 450 \\ (18 \times \frac{75}{4} ) + 15y = 450 \\ \frac{1350}{4} + 15y = 450 \\ 15y = 450 - \frac{1350}{4} \\ 15y = \frac{1800 - 1350}{4} \\ 15y = \frac{450}{4} \\ y = \frac{450}{4} \div 15 \\ y = \frac{ _{30 \: \: \: } \cancel{ 450}}{4} \times \frac{1}{ \cancel{ 15}_{ \: \: \: 1}} \\ \boxed{ \large y = \underline{ \underline{ \bf \frac{30}{4} }}}$