Question 536511
{{{4s-5t=18}}}.........(1)
{{{6s+10t=-8}}}...........(2)

Take (2)
{{{6s+10t=-8}}}
{{{2(3s+5t)=-8}}}
Divide by 2 both sides
{{{2(3s+5t)/2=-8/2}}}
{{{3s+5t=-4}}}...............(3)
Add (1) and (3)
{{{4s-5t=18}}}
{{{3s+5t=-4}}}
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{{{7s=14}}}
Divide by 7 both sides
{{{7s/7=14/7}}}
{{{s=2}}}
Put the value of s in (1)
{{{4s-5t=18}}}.........(1)
{{{4(2)-5t=18}}}
{{{8-5t=18}}}
{{{-5t=18-8}}}
{{{-5t=18-8}}}
{{{-5t=10}}}
Divide by -5 both sides
{{{-5t/-5=10/-5}}}
{{{t=-2}}}

(s,t)=(2,-2)


Check
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Put the values of x and y in (2)
{{{6(2)+10(-2)=-8}}}
{{{12-20=-8}}}
{{{-8=-8}}}